BRIP1 (FANCJ / BACH1) review notes

UniProt: Q9BX63 (FANCJ_HUMAN). Gene: BRIP1 (HGNC:20473). Synonyms: BACH1, FANCJ.
1249 aa. EC 5.6.2.3. Family: DEAD/DEAH box helicase, Rad3/XPD (DinG) subfamily.

Identity / disambiguation (IMPORTANT)

BRIP1's old alias BACH1 ("BRCA1-associated C-terminal helicase 1") collides with a
completely different gene, BACH1 = BTB and CNC homology 1 (bZIP/BTB transcription
factor, transcriptional repressor of heme oxygenase-1; UniProt O14867). These are
unrelated proteins.

• PMID:14504288 ("Cadmium induces nuclear export of Bach1, a transcriptional repressor
  of heme oxygenase-1 gene") is about the transcription factor BACH1 (O14867), NOT
  BRIP1/FANCJ. The abstract concerns Bach1/small Maf heterodimers, ho-1 repression, Nrf2
  competition, Crm1/Exportin-1-dependent nuclear export — zero helicase/DNA-repair content.
  PMID:14504288. The three GOA annotations sourced from this PMID
  (nucleus IDA, cytoplasm IDA, and regulation of transcription by RNA polymerase II
  GO:0006357 IDA, all MGI-assigned) are mis-mapped via the BACH1 alias.
• GO:0006357 (regulation of transcription by RNA Pol II) is uniquely from this paper and is
  biologically wrong for the FANCJ helicase → REMOVE.
• nucleus/cytoplasm are coincidentally correct for BRIP1 (supported by valid refs), so those
  terms are retained overall, but this particular evidence line is flagged as mis-attributed.

Core molecular function

5'-3' ATP-dependent DNA helicase; DNA-dependent ATPase; requires a [4Fe-4S] cluster.
- PMID:14983014
- PMID:14983014 (DNA-dependent ATPase; K52R catalytic-dead)
- PMID:14983014
- Catalytic activity (UniProt): EC 5.6.2.3 "Couples ATP hydrolysis with the unwinding of duplex
DNA at the replication fork by translocating in the 5'-3' direction."
- Cofactor [4Fe-4S] cluster required for helicase activity: PMID:20639400;
UniProt DOMAIN "4Fe-4S iron-sulfur-binding is required for helicase activity"
(PMID:16973432 "The DNA repair helicases XPD and FancJ have essential iron-sulfur domains").
- DNA substrate specificity: prefers forked duplex; needs a minimal 5' ssDNA tail of ~15 nt;
can release D-loop third strand; fails on Holliday junctions.
PMID:15878853

G-quadruplex unwinding

• PMID:18426915
• PMID:18426915
• PMID:18426915

DNA-protein crosslink (DPC) repair at replication forks

• PMID:36608669
• Acts at the replication fork (IDA, PMID:36608669).

Homologous recombination / DSB repair / BRCA1

• PMID:11301010
• PMID:11301010
• BRCA1 binding requires phospho-Ser990: PMID:14576433 (BRCT is a phospho-peptide binding domain;
  UniProt: "Phosphorylation is necessary for interaction with BRCA1, and is cell-cycle regulated").
• Part of the BRCA1-B complex (ComplexPortal CPX-4426): GO:0070532, PMID:16391231.

Interstrand crosslink (ICL) repair / MutLalpha (MLH1)

• PMID:17581638
• PMID:17581638
• FANCJ acts late in the FA pathway, after FANCD2 ubiquitination (UniProt, PMID:16153896/14983014).

Other interactions

• BLM helicase: PMID:21240188
• RPA (RPA1/RPA70): PMID:17596542
• CIA machinery (CIAO1, CIAO2B/FAM96B, MMS19) — cytosolic Fe-S cluster assembly / maturation of
  the FANCJ Fe-S cluster: PMID:23585563 (interaction with CIAO1, CIAO2B and MMS19; UniProt SUBUNIT).
• Acetylation at K1249 regulates DDR: PMID:22792074 (UniProt PTM "Acetylation at Lys-1249
  facilitates DNA end processing required for repair and checkpoint signaling").

Protein-binding (GO:0005515) IPI annotations

All IntAct/UniProt IPI protein-binding lines (BRCA1 P38398, MLH1 P40692, BLM P54132,
MMS19 Q96T76, HSD17B14 Q9BPX1) are uninformative MF (GO:0005515). Per curation guidelines,
marked MARK_AS_OVER_ANNOTATED; the biologically meaningful partners (BRCA1, MLH1, BLM, MMS19/CIA)
are captured in core_functions and BP annotations.

Localization

Nucleus (core; nucleoplasm), functions at replication fork. Also cytoplasm (CIA/Fe-S maturation,
PMID:23585563). Nuclear membrane (HPA IDA GO:0031965) is a single HPA-antibody localization not
corroborated functionally → over-annotated. Testis-high expression (UniProt tissue specificity).

Disease

Biallelic loss → Fanconi anemia complementation group J (FANCJ, MIM:609054); monoallelic variants
→ breast/ovarian cancer susceptibility (BC MIM:114480). FANCJ variants A349P (Fe-S), K52R
(Walker A, catalytic-dead), P47A/M299I (breast cancer, helicase-defective).

NER (GO:0006289) IBA

No FANCJ-specific evidence for classical nucleotide-excision repair; the IBA propagates the
Rad3/XPD family function (XPD does NER) onto FANCJ. FANCJ's characterized roles are ICL/HR/DPC/G4,
not NER → MARK_AS_OVER_ANNOTATED.

NEW annotations added

• GO:0036297 interstrand cross-link repair (BP) — FANCJ's central biological role
  (PMID:17581638, PMID:18426915; UniProt DISEASE/FUNCTION).
• GO:0051539 4 iron, 4 sulfur cluster binding (MF) — experimentally required cofactor
  (PMID:20639400, PMID:16973432; UniProt COFACTOR/BINDING).