Involved in ribosomal large subunit assembly (By similarity). S-adenosyl-L-methionine-dependent methyltransferase that may methylates the C(5) position of cytosine in rRNA (By similarity). May play a role in the regulation of the cell cycle and the increased nucleolar activity that is associated with the cell proliferation (By similarity). Seems involved in the regulation of cell proliferation (By similarity). a cytidine in rRNA + S-adenosyl-L-methionine = a 5-methylcytidine in rRNA + H(+) + S-adenosyl-L-homocysteine Normal levels of methylation at cytosine 2860 of 25S rRNA. Belongs to the class I-like SAM-binding methyltransferase superfamily. RsmB/NOP family.