InterPro-to-GO mappings assign chromatin binding (IPR001025, BAH domain) and methyltransferase activity (IPR001525, C5 methyltransferase) to MET1A based on its DNMT1-like domain architecture.

The CpG-island-mediated negative-regulation annotation (GO:0044027) was transferred by ISS from human DNMT1 (UniProtKB:P34881); the mammalian CpG-island framing maps only loosely onto plant genome methylation.

Core DNMT1/MET1 functions (nucleus, DNA binding, DNA cytosine-5 methyltransferase activity) are conserved across the phylogenetic group and propagated to MET1A by IBA.

SwissProt keyword-derived (SPKW) annotations present in the Sept 2025 goa_uniprot_gcrp snapshot but removed from the current GOA release after GOA retired the keyword2GO pipeline for cellular organisms.

For MET1A, the keyword "Methyltransferase" mapped to the bare process term "methylation" (GO:0032259), which drops the substrate (DNA) and the C5-cytosine / maintenance specificity; the substrate-specific process is GO:0141119.

Nuclear localization (SL-0191) mapped to GO:0005634; consistent with the IBA nucleus annotation and the role of a chromosomal-DNA maintenance methyltransferase.

ARBA model assigned "negative regulation of gene expression, epigenetic" (GO:0045814), a downstream pleiotropic consequence of MET1-mediated CG methylation.

Combined IEA methods (RHEA:13681 / EC 2.1.1.37) assign the core molecular function DNA (cytosine-5-)-methyltransferase activity (GO:0003886).

OsMET1-1 (MET1A) and OsMET1-2 each encode a cytosine-5 DNA methyltransferase of the Dnmt1/MET1 class, with two-thirds regulatory and one-third catalytic domain.

Steady-state OsMET1-2 mRNA is 7- to 12-fold higher than OsMET1-1 in callus, root and inflorescence, indicating OsMET1a is the minor, lower-expressed paralog.

RNAi knockdown of OsMET1-1 reactivated a silenced 35S-uidA-nos transgene in rice callus, consistent with inactivation of maintenance methylation and the involvement of methylation in transcriptional silencing.

Large-scale rice full-length cDNA collection, sequencing, genome-mapping and InterPro-based annotation paper; not a gene-specific functional study for MET1A.

MET1A (OsMET1a / OsMET1-1; LOC_Os03g58400) is a DNMT1-like maintenance DNA (cytosine-5) methyltransferase (EC 2.1.1.37) that transfers a methyl group to the C5 position of cytosine in DNA, primarily maintaining symmetric CG methylation after replication.

Rice CG methylation is mainly maintained by MET1 enzymes (OsMET1a and OsMET1b); OsMET1b is the dominant, more highly expressed paralog, and an OsMET1-1 knock-in mutant showed no discernible developmental phenotype, indicating a minor/redundant role for OsMET1a.

Loss of the major paralog OsMET1b collapses gene-body mCG from 27.35% to 3.95% (~86% loss), reduces transposon mCG ~77%, derepresses transposons, and co-induces OsMET1a ~2.5-fold and a VIM-family cofactor ~4.5-fold, placing OsMET1a in the CG-maintenance machinery and its buffering responses.

A maintenance DNA methyltransferase acting on chromosomal DNA is most plausibly nuclear; no direct OsMET1a localization or in vitro substrate-preference assay was retrieved, so these are inferences from enzyme class and orthology.