C1orf77, also known as Friend of PRMT1 protein, is a 248 amino acid protein that plays an essential role in the ligand-dependent activation of estrogen receptor target genes. C1orf77 is tightly associated with chromatin and is modified by both asymmetric and symmetric arginine methylation. Depletion of C1orf77 results in almost complete block of estradiol-induced promter occupancy by the estrogen receptor. Also, complete knockdown of C1orf77 mRNA in adult erythroid progenitors stongly induces fetal hemoglobin, suggesting that C1orf77 is a critical modulator of γ-globin gene expression. There are two isoforms of C1orf77 that are produced as a result of alternative splicing events. The gene encoding C1orf77 maps to human chromosome 1, the largest human chromosome spanning about 260 million base pairs and making up 8% of the human genome. There are about 3,000 genes on chromosome 1, and considering the great number of genes there are also a large number of diseases associated with chromosome 1.