N-terminal domain of Oryza sativa transcription factor SUPPRESSOR OF FRI 4 (OsSUF4), Arabidopsis thaliana SUF4 (AtSUF4), and similar proteins
Oryza sativa SUPPRESSOR OF FRI 4 (OsSUF4) is a C2H2-type zinc finger transcription factor which interacts with the major H3K36 methyltransferase SDG725 to promote H3K36me3 (tri-methylation at H3K9) establishment. The transcription factor OsSUF4 recognizes a specific 7-bp DNA element (5'-CGGAAAT-3'), which is contained in the promoter regions of many genes throughout the rice genome. Through interaction with OsSUF4, SDG725 is recruited to the promoters of key florigen genes, RICE FLOWERING LOCUS T1 (RFT1) and Heading date 3a (Hd3a), for H3K36 deposition to promote gene activation and rice plant flowering. OsSUF4 target genes include a number of genes involved in many biological processes. Flowering plant Arabidopsis SUF4 binds to a 15bp DNA element (5'-CCAAATTTTAAGTTT-3') within the promoter of the floral repressor gene FLOWERING LOCUS C (FLC) and recruits the FRI-C transcription activator complex to the FLC promoter. Although the DNA-binding element and target genes of AtSUF4 are different from those of OsSUF4, AtSUF4 is known to interact with the Arabidopsis H3K36 methyltransferase SDG8 (also known as ASHH2/EFS/SET8), and the methylation deposition mechanism mediated by the SUF4 transcription factor and H3K36 methyltransferase may be conserved in Arabidopsis and rice. Proteins in this family have two conserved C2H2-type zinc finger motifs at the N-terminus (included in this model), and a large proline-rich domain at the C-terminus; for OsSUF4, it has been shown that the N-terminal zinc-finger domain is responsible for DNA binding, and that the C-terminal domain interacts with SDG725.