mcm-4 (also known as lin-6 and let-358) encodes the Caenorhabditis elegans ortholog of MCM4, one of the six AAA+ ATPase subunits of the MCM2-7 heterohexamer. MCM2-7 is the motor of the eukaryotic replicative helicase. It is loaded onto replication origins as an inactive double hexamer to license them, and at S phase it is activated with CDC45 and GINS into the CMG helicase that unwinds template DNA. Helicase and ATPase activity belong to the assembled ring: each of its six ATP sites pairs one subunit's Walker A/B motifs with the arginine finger of its neighbour, and MCM-4 keeps these catalytic motifs. In C. elegans, MCM-4 is expressed in all dividing cells, is nuclear in interphase, leaves condensed mitotic chromosomes, and reassociates with chromatin in late anaphase, the expected licensing window. Loss of zygotic mcm-4 abolishes DNA synthesis in postembryonic somatic lineages while those cells still enter mitosis, so mitotic entry is no longer coupled to completed replication. mcm-4 is also needed for the S-phase checkpoint delay caused by reduced ribonucleotide reductase in embryos. Germline replication continues longer in mutants, probably on maternal product. MCM-4 acts cell-autonomously in DNA synthesis and intestinal endoreduplication, and its expression in the epidermis alone rescues the growth retardation and larval lethality of mutants. The biochemical activities (ATP hydrolysis, ssDNA binding, helicase) are inferred from orthology and conserved motifs. They have not been measured for the C. elegans protein.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0042555 MCM complex | IBA GO_REF:0000033 | ACCEPT | Summary: MCM-4 is a subunit of the heterohexameric MCM2-7 (MCM) complex. The IBA is placed at PTN000179711, the PAINT node for the replicative MCM2-7 clade, which C. elegans MCM-4 (PANTHER PTHR11630:SF66, MCM4 subfamily) descends from; the identity of lin-6 as the MCM4 ortholog was established in C. elegans. Reason: Core component. The PAINT node covers MCM2-7 subunits from yeast to mammals, MCM-4 sits inside that clade, and nothing indicates loss of complex membership. The C. elegans paper identifies MCM-4 as an MCM2-7 subunit by orthology; physical incorporation of C. elegans MCM-4 into the hexamer has not itself been shown biochemically. Supporting Evidence: PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. file:worm/mcm-4/mcm-4-uniprot.txt Belongs to the MCM family. |
| GO:0003697 single-stranded DNA binding | IBA GO_REF:0000033 | ACCEPT | Summary: Single-stranded DNA binding is a conserved property of the MCM2-7 ring, which encircles and translocates along the leading-strand template during unwinding. The IBA comes from PTN000179711 (MCM2-7 clade), seeded by yeast Mcm4 (SGD:S000006223). Reason: Inherited from the MCM2-7 ancestral node, inside which MCM-4 sits. No C. elegans biochemistry exists; the claim rests on phylogeny plus the conserved MCM OB-fold and AAA+ modules. As with the helicase, the activity is exercised within the hexamer. Supporting Evidence: PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. file:worm/mcm-4/mcm-4-uniprot.txt Belongs to the MCM family. |
| GO:0017116 single-stranded DNA helicase activity | IBA GO_REF:0000033 | ACCEPT | Summary: MCM-4 contributes to the single-stranded DNA helicase activity of the MCM2-7/CMG helicase. The contributes_to qualifier correctly attributes the activity to the assembled ring. PAINT placed this at PTN000179711 (MCM2-7 clade) from experimental evidence on the yeast and fission yeast MCM subunits. Reason: Core molecular function, inferred by phylogeny (not tested in C. elegans). The catalytic Walker A/B and arginine-finger motifs are intact in MCM-4, so there is no sign of the subunit-level divergence that would argue against inheritance. Supporting Evidence: PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. file:worm/mcm-4/mcm-4-bioinformatics/RESULTS-rereview.md the Walker A lysine (K475) and Walker B acidic residues (D533, E534) are retained, and the SRF arginine-finger motif is present PMID:31283754 is the DNA helicase complex responsible for unwinding the DNA at the origins of replication file:worm/mcm-4/mcm-4-deep-research-falcon.md MCM proteins carry ATP-binding motifs and are attributed ATPase and helicase activities, with ATP hydrolysis within the MCM ring driving DNA translocation and unwinding in CMG. |
| GO:0006271 DNA strand elongation involved in DNA replication | IBA GO_REF:0000033 | ACCEPT | Summary: The MCM2-7 ring is the motor of the CMG helicase that unwinds DNA at moving forks, so the complex takes part in strand elongation directly. The IBA is from PTN000179968 (eukaryotic MCM4 subfamily node), seeded by yeast Mcm4. Reason: The participation test is met: the MCM ring does the unwinding work at the fork. In C. elegans, loss of mcm-4 abolishes postembryonic somatic DNA synthesis, which agrees with this but cannot separate an initiation defect from an elongation defect; the elongation role itself rests on the phylogenetic inference. Supporting Evidence: PMID:21146520 C. elegans lin-6 mutants lack DNA synthesis in postembryonic somatic cell lineages, while entry into mitosis continues PMID:21146520 This result confirms that mcm-4 acts cell-autonomously in DNA synthesis and endoreduplication cycles. |
| GO:1902975 mitotic DNA replication initiation | IBA GO_REF:0000033 | ACCEPT | Summary: Origin licensing (MCM2-7 loading as an inactive double hexamer) and its activation into CMG are the core events of replication initiation. The IBA comes from PTN000179968 (MCM4 subfamily), seeded by S. pombe Mcm4 (cdc21). Reason: Core process. C. elegans data are consistent with it: MCM-4 associates with chromatin in late anaphase, the expected window for origin licensing, and mcm-4 loss blocks DNA synthesis while mitosis continues. Supporting Evidence: PMID:21146520 MCM-4 remained cytoplasmic at the onset of anaphase; however, chromatin association became apparent in late anaphase PMID:21146520 Our results support a conserved function of mcm-4 in replication licensing, DNA synthesis and the replication checkpoint |
| GO:0000727 double-strand break repair via break-induced replication | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Break-induced replication uses the replicative MCM2-7 helicase to copy DNA from an invading broken end. PAINT placed this term at the eukaryotic MCM4 subfamily node PTN000179968 based on yeast Mcm4 (SGD:S000006223) experimental data. Reason: The earlier MARK_AS_OVER_ANNOTATED is revised. An IBA has to be challenged on its node placement. MCM-4 sits inside the MCM4 subfamily clade, there is no evidence of divergence, and the MCM helicase does the unwinding work during BIR, so the participation test is met. What is missing is C. elegans-specific evidence, which is not grounds for overturning a phylogenetic inference. The term is a correct but peripheral use of the core replicative helicase activity, so it is kept as non-core. Supporting Evidence: file:worm/mcm-4/mcm-4-uniprot.txt Belongs to the MCM family. PMID:21146520 Our results support a conserved function of mcm-4 in replication licensing, DNA synthesis and the replication checkpoint |
| GO:0003677 DNA binding | IEA GO_REF:0000002 | MODIFY | Summary: DNA binding (InterPro2GO) is correct but less specific than the single-stranded DNA binding the gene already carries via IBA and ISS. Reason: The term is correct but general. The supported, more specific descendant GO:0003697 single-stranded DNA binding is already on this gene, so refine to that term. Proposed replacements: single-stranded DNA binding Supporting Evidence: file:worm/mcm-4/mcm-4-uniprot.txt Belongs to the MCM family. PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. |
| GO:0003678 DNA helicase activity | IEA GO_REF:0000120 | MODIFY | Summary: Generic DNA helicase activity, asserted with "enables". For an MCM subunit, the supported activity is the single-stranded DNA (3'-5' translocating) helicase activity of the assembled MCM2-7 ring, which the gene already carries as contributes_to GO:0017116 via IBA. Reason: The term is correct but general. GO:0017116 is a descendant of GO:0003678 (checked in OLS) and is already on the gene, so refine to it. The qualifier also matters: an isolated MCM4 chain is not a helicase, so the activity should be read as contributes_to, as in the IBA and ISS rows. Proposed replacements: single-stranded DNA helicase activity Supporting Evidence: PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. file:worm/mcm-4/mcm-4-uniprot.txt The active ATPase sites in the mcm2-7 ring are formed through the interaction surfaces of two neighboring subunits PMID:31283754 is the DNA helicase complex responsible for unwinding the DNA at the origins of replication file:worm/mcm-4/mcm-4-deep-research-falcon.md an MCM4/6/7 subcomplex exhibits intrinsic ssDNA-dependent ATP hydrolysis |
| GO:0005524 ATP binding | IEA GO_REF:0000002 | ACCEPT | Summary: MCM-4 carries a conserved AAA+ ATPase module. Its Walker A motif (GDPGTSKS, 469-476) and the curated ATP-binding residues lie in this subunit, and ATP binding at these sites powers the MCM2-7 motor. Reason: Correct and specific. The Walker A/B motifs are intact (bioinformatics re-check). ATP binding takes place on this subunit's own P-loop, although the arginine finger that completes each catalytic site comes from the neighbouring subunit. Supporting Evidence: file:worm/mcm-4/mcm-4-bioinformatics/RESULTS-rereview.md the Walker A lysine (K475) and Walker B acidic residues (D533, E534) are retained, and the SRF arginine-finger motif is present file:worm/mcm-4/mcm-4-uniprot.txt The active ATPase sites in the mcm2-7 ring are formed through the interaction surfaces of two neighboring subunits |
| GO:0005694 chromosome | IEA GO_REF:0000044 | MODIFY | Summary: Chromosome localization from UniProt SubCell mapping. In C. elegans the experimental observation is chromatin association: MCM-4 binds chromatin from late anaphase onward and is excluded from condensed prophase and metaphase chromosomes. Reason: The term is correct but general. The observation in the paper is chromatin association, so refine to GO:0000785 chromatin (part_of chromosome, checked in OLS). Proposed replacements: chromatin Supporting Evidence: PMID:21146520 MCM-4 remained cytoplasmic at the onset of anaphase; however, chromatin association became apparent in late anaphase |
| GO:0006260 DNA replication | IEA GO_REF:0000002 | MODIFY | Summary: DNA replication is correct but general. The gene already carries the more specific supported processes: mitotic DNA replication initiation and DNA strand elongation involved in DNA replication (and premeiotic DNA replication, kept as non-core). Reason: The term is true but general, and the specific descendants supported by phylogeny and by the C. elegans loss-of-function data are already on the gene. Both are listed as replacements because MCM2-7 acts in both initiation and elongation. Proposed replacements: mitotic DNA replication initiation DNA strand elongation involved in DNA replication Supporting Evidence: PMID:21146520 C. elegans lin-6 mutants lack DNA synthesis in postembryonic somatic cell lineages, while entry into mitosis continues PMID:21146520 Our results support a conserved function of mcm-4 in replication licensing, DNA synthesis and the replication checkpoint |
| GO:0006270 DNA replication initiation | IEA GO_REF:0000002 | MODIFY | Summary: DNA replication initiation (InterPro2GO) is correct. The gene already carries the more specific IBA term mitotic DNA replication initiation. Reason: Refine to GO:1902975, an is_a descendant of GO:0006270 (checked in OLS) that the gene already carries. MCM-4 also likely acts in premeiotic replication initiation, which is covered by the separate premeiotic DNA replication row. Proposed replacements: mitotic DNA replication initiation Supporting Evidence: PMID:21146520 MCM-4 remained cytoplasmic at the onset of anaphase; however, chromatin association became apparent in late anaphase PMID:21146520 Our results support a conserved function of mcm-4 in replication licensing, DNA synthesis and the replication checkpoint |
| GO:0016887 ATP hydrolysis activity | IEA GO_REF:0000116 | ACCEPT | Summary: ATP hydrolysis (Rhea-mapped, RHEA:13065) driven by the MCM AAA+ module powers DNA translocation and unwinding by the MCM2-7 ring. Reason: Correct and core to the mechanism. The catalytic Walker A lysine and Walker B DE residues of MCM-4 are intact. Each catalytic site is completed in trans by a neighbour's arginine finger, so the activity is exercised in the hexamer. No C. elegans ATPase assay exists; the claim rests on conserved catalytic residues and orthology to MCM4. Supporting Evidence: file:worm/mcm-4/mcm-4-bioinformatics/RESULTS-rereview.md the Walker A lysine (K475) and Walker B acidic residues (D533, E534) are retained, and the SRF arginine-finger motif is present file:worm/mcm-4/mcm-4-uniprot.txt The active ATPase sites in the mcm2-7 ring are formed through the interaction surfaces of two neighboring subunits file:worm/mcm-4/mcm-4-deep-research-falcon.md MCM proteins carry ATP-binding motifs and are attributed ATPase and helicase activities, with ATP hydrolysis within the MCM ring driving DNA translocation and unwinding in CMG. |
| GO:0042555 MCM complex | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro2GO (IPR008047, MCM4 family) annotation to MCM complex. It agrees with the IBA, ISS and NAS rows for the same term. Reason: Correct core component; MCM4-family membership is good support for MCM2-7 complex membership. Supporting Evidence: file:worm/mcm-4/mcm-4-uniprot.txt Belongs to the MCM family. PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. |
| GO:0005694 chromosome | EXP PMID:21146520 C. elegans MCM-4 is a general DNA replication and checkpoint... | MODIFY | Summary: Direct observation (immunostaining) in C. elegans embryos: MCM-4 is not on condensed prophase or metaphase chromosomes, becomes chromatin-associated in late anaphase, and stays nuclear through interphase. This is regulated chromatin loading, consistent with origin licensing. Reason: The experimental observation supports the more specific term GO:0000785 chromatin (part_of chromosome). This is a refinement, not a challenge to the curator: the localization is accepted and expressed at the precision the paper reports. Proposed replacements: chromatin Supporting Evidence: PMID:21146520 MCM-4 remained cytoplasmic at the onset of anaphase; however, chromatin association became apparent in late anaphase PMID:21146520 MCM-4 was not chromatin-associated during Meiosis I of the fertilized oocyte, and the first polar body did not contain MCM-4 file:worm/mcm-4/mcm-4-deep-research-falcon.md MCM-4 is nuclear during interphase, becomes diffuse upon nuclear envelope breakdown and is not associated with metaphase chromatin, and then reassociates with chromatin in late anaphase |
| GO:0016887 ATP hydrolysis activity | ISS GO_REF:0000024 | ACCEPT | Summary: ATP hydrolysis transferred by curator judgement (ISS) from mouse MCM4 (P49717), whose MCM4/6/7 subcomplex has measured ATPase/helicase activity. MCM-4 is in the same PANTHER subfamily (PTHR11630:SF66, MCM4) as the donor, so the transfer is evolutionarily grounded. Reason: Consistent with the Rhea IEA row for the same term. The donor and target are in the same subfamily and the catalytic motifs are conserved. Supporting Evidence: file:worm/mcm-4/mcm-4-bioinformatics/RESULTS-rereview.md the Walker A lysine (K475) and Walker B acidic residues (D533, E534) are retained, and the SRF arginine-finger motif is present file:worm/mcm-4/mcm-4-uniprot.txt The active ATPase sites in the mcm2-7 ring are formed through the interaction surfaces of two neighboring subunits |
| GO:0006279 premeiotic DNA replication | NAS PMID:21146520 C. elegans MCM-4 is a general DNA replication and checkpoint... | KEEP AS NON CORE | Summary: The NAS row asserts a role in premeiotic DNA replication. The C. elegans paper shows MCM-4 is strongly nuclear in the germline and absent from chromatin in meiosis I (no S phase between the meiotic divisions). It does not directly test premeiotic S phase, because the zygotic mutant germline continues replicating, probably on maternal product. Reason: Participation is mechanistically sound: MCM2-7 is the replicative helicase in premeiotic S phase across eukaryotes. Direct C. elegans evidence is limited, and this is one context of the general replication function, so it is kept as non-core. Supporting Evidence: PMID:21146520 Immunostaining of wild-type animals for MCM-4 showed strong nuclear staining in the gonad, embryos and postembryonic lineages PMID:21146520 In lin-6 mutants, only cells in the germline continued DNA replication |
| GO:0042555 MCM complex | NAS PMID:21146520 C. elegans MCM-4 is a general DNA replication and checkpoint... | ACCEPT | Summary: Curator statement (NAS) from the paper identifying MCM-4 as an MCM2-7 subunit. Reason: Correct core component, consistent with the IBA, IEA and ISS rows for the same term. Supporting Evidence: PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. |
| GO:0003678 DNA helicase activity | ISS GO_REF:0000024 | MODIFY | Summary: DNA helicase activity (contributes_to) transferred by ISS from mouse MCM4 (same PANTHER subfamily SF66). The qualifier is right; the term is less specific than the ssDNA helicase activity the gene already carries via IBA. Reason: The term is correct but general. Refine to GO:0017116 single-stranded DNA helicase activity (a descendant of GO:0003678, already on this gene), keeping contributes_to. Proposed replacements: single-stranded DNA helicase activity Supporting Evidence: PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. file:worm/mcm-4/mcm-4-uniprot.txt The active ATPase sites in the mcm2-7 ring are formed through the interaction surfaces of two neighboring subunits |
| GO:0003697 single-stranded DNA binding | ISS GO_REF:0000024 | ACCEPT | Summary: ssDNA binding (contributes_to) transferred from mouse MCM4 (P49717; same subfamily). It matches the IBA row for the same term. Reason: Correct. The contributes_to qualifier reflects DNA engagement by the assembled ring. Supporting Evidence: PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. file:worm/mcm-4/mcm-4-uniprot.txt Belongs to the MCM family. |
| GO:0042555 MCM complex | ISS GO_REF:0000024 | ACCEPT | Summary: MCM complex membership transferred from mouse MCM4 (P49717; same subfamily PTHR11630:SF66). Reason: Correct core component, consistent with the other MCM complex rows. Supporting Evidence: PMID:21146520 lin-6 corresponds to mcm-4 and encodes an evolutionarily conserved component of the MCM2-7 pre-RC and replicative helicase complex. |
| GO:0005515 protein binding | IPI PMID:31283754 The demethylase NMAD-1 regulates DNA replication and repair ... | REMOVE | Summary: IPI to NMAD-1 (Q8MNT9): MCM-4 was a candidate in NMAD-1 IP/MS and bound NMAD-1 directly in vitro, but the authors could not confirm the interaction in vivo. Reason: Removed under the GO:0005515 policy because bare protein binding carries no functional information. Removal does not mean the reported in vitro interaction is false. No more informative MF term is supported, since the paper does not show what the binding does for MCM-4. Supporting Evidence: PMID:31283754 NMAD-1 directly bound to MTSS-1, TOP-2, and MCM-4, components of the DNA replication machinery |
| GO:0007399 nervous system development | IMP PMID:7262539 Isolation and genetic characterization of cell-lineage mutan... | MARK AS OVER ANNOTATED | Summary: IMP from the original postembryonic cell-lineage screen, where lin-6(e1466) (= mcm-4) was isolated. The lineage defects in neuronal precursors follow from failed DNA synthesis in dividing blast cells, which still enter mitosis. Reason: MCM-4 does none of the work of nervous system development. It replicates DNA in dividing precursors, and the lineage phenotype is a downstream consequence of that general requirement (necessity, not participation). The full text of the cloning paper (PMID:21146520) shows mutant cells keep their temporal and differentiation programmes but lack DNA synthesis. The IMP observation is not disputed (the original paper is abstract-only here), but the process term over-interprets it. Supporting Evidence: PMID:21146520 C. elegans lin-6 mutants lack DNA synthesis in postembryonic somatic cell lineages, while entry into mitosis continues PMID:21146520 Induction of cell cycle entry and differentiation continues in developing mcm-4 larvae, even in cells that went through abortive division. |
| GO:0008406 gonad development | IMP PMID:7262539 Isolation and genetic characterization of cell-lineage mutan... | MARK AS OVER ANNOTATED | Summary: IMP from the lin-6(e1466) cell-lineage screen. In the mutant the gonad is actually the tissue that keeps replicating DNA longest, and the somatic gonad and germline cope substantially with loss of zygotic mcm-4. Reason: Gonad development defects are a downstream consequence of the general DNA replication requirement in dividing cells, not participation in gonad development. The phenotype is not disputed; the process annotation over-interprets it. Supporting Evidence: PMID:21146520 the somatic gonad and germline show substantial ability to cope with lack of zygotic mcm-4 function |
| GO:0040011 locomotion | IMP PMID:7262539 Isolation and genetic characterization of cell-lineage mutan... | MARK AS OVER ANNOTATED | Summary: IMP to locomotion from the lin-6(e1466) screen. Mutants grow slowly, arrest or die as larvae, or become sterile adults. Any movement defect is a whole-organism consequence of failed postembryonic cell divisions. Reason: Locomotion is a distal organismal phenotype; MCM-4 does no work in the locomotion process. The underlying IMP observation is not disputed, but the term is an over-interpretation of a pleiotropic replication defect. Supporting Evidence: PMID:21146520 These mutants grow slowly and either die during larval development or develop into sterile adults |
| GO:0005634 nucleus | IDA PMID:21146520 C. elegans MCM-4 is a general DNA replication and checkpoint... | ACCEPT | Summary: Direct immunostaining and MCM-4::mCherry imaging in C. elegans show nuclear MCM-4 in dividing cells of the gonad, embryo and postembryonic lineages. The signal disperses at nuclear envelope breakdown and returns to chromatin in late anaphase. Reason: Experimentally established in C. elegans; antibody specificity was confirmed by RNAi and by the mutant. Supporting Evidence: PMID:21146520 Immunostaining of wild-type animals for MCM-4 showed strong nuclear staining in the gonad, embryos and postembryonic lineages PMID:21146520 This staining was MCM-4-specific, as RNAi of mcm-4 eliminated the nuclear signal in the germline and embryos file:worm/mcm-4/mcm-4-deep-research-falcon.md MCM-4 is nuclear during interphase, becomes diffuse upon nuclear envelope breakdown and is not associated with metaphase chromatin, and then reassociates with chromatin in late anaphase |
| GO:0005634 nucleus | IBA GO_REF:0000033 | ACCEPT | Summary: IBA is_active_in nucleus from PTN000179712, a node covering MCM2-7 and related MCM proteins, with many experimental donors including the other C. elegans MCM genes (WBGene00003154, WBGene00003155) and mcm-4 itself (WBGene00003156). Reason: MCM-4's own nuclear IDA is one of the descendant evidences behind this IBA, so its appearance in WITH/FROM is expected and not circular. Correct and consistent with the direct C. elegans observation. Supporting Evidence: PMID:21146520 Immunostaining of wild-type animals for MCM-4 showed strong nuclear staining in the gonad, embryos and postembryonic lineages |
| GO:0005634 nucleus | IEA GO_REF:0000120 | ACCEPT | Summary: Combined automated (ARBA plus SubCell) nucleus annotation. Correct and consistent with the direct C. elegans IDA. Reason: Correct localization, independently established by immunostaining in C. elegans. Supporting Evidence: PMID:21146520 Immunostaining of wild-type animals for MCM-4 showed strong nuclear staining in the gonad, embryos and postembryonic lineages |
Loading supporting content…
Download this section (compressed HTML)Q: Does the apparent tolerance of the C. elegans germline and somatic gonad to loss of zygotic mcm-4 reflect maternal MCM-4 contribution, or a genuinely lower requirement for MCM-4 in those lineages?
Q: What is the functional significance of the physical interaction between MCM-4 and the DNA demethylase NMAD-1 (and TOP-2) for replication or repair in the germline?
Q: Why is epidermal (hypodermal) expression of MCM-4 specifically sufficient to rescue organismal growth and viability, given that MCM-4 is expressed in all dividing cells?
Q: Does MCM-4, as an obligate subunit of the CMG helicase, contribute to the proposed replication-independent / chromatin-handling role of CMG in asymmetric cell-fate divergence (reported for the GINS subunit PSF-2), or is that function genetically separable from MCM-4?
Q: Is the C. elegans requirement for mcm-4 in the S-phase checkpoint delay a direct signalling role, or does it simply reflect that, without licensed and fired origins, no stalled forks exist to produce the checkpoint signal? GO has no annotation for this, and none is proposed here.
Experiment: Reconstitute or affinity-purify the C. elegans MCM2-7 / CMG complex and measure ATP-dependent single-stranded DNA helicase and ATPase activity to directly confirm MCM-4 incorporation and biochemical function.
Hypothesis: C. elegans MCM-4 assembles into a functional MCM2-7/CMG complex with ATP-dependent DNA helicase activity, as predicted from orthology.
Experiment: Use tissue-specific degron/auxin-inducible depletion of MCM-4 (germline vs. hypodermis vs. neurons) to dissect lineage-specific replication requirements and separate the primary replication defect from downstream developmental phenotypes.
Hypothesis: The developmental (nervous system, gonad, locomotion) phenotypes are secondary to loss of DNA replication in dividing precursors rather than a tissue-specific molecular function of MCM-4.
Experiment: Map the MCM-4/NMAD-1 interaction interface and test whether NMAD-1 demethylase activity modulates MCM-4 chromatin loading or replication/repair in the germline.
Hypothesis: NMAD-1 regulates MCM-4-dependent replication/repair in the germline through a direct physical interaction.
Loading supporting content…
Download this section (compressed HTML)mcm-4 encodes a member of the MCM2/3/5 family with similarity to human MCM4 minichromosome maintenance deficient 4 protein, and affects embryonic viability, nuclear morphology in early embryos, and larval viability.
Loading supporting content…
Download this section (compressed HTML)Loading supporting content…
Download this section (compressed HTML)