A methylase that recognizes the double-stranded sequence 5'-GGWCC-3', methylates C-? on both strands, and protects the DNA from cleavage by the HgiBI endonuclease (PubMed:12654995). This system is less active than isoschizomeric RM.HgiEI (PubMed:7607523). a 2'-deoxycytidine in DNA + S-adenosyl-L-methionine = a 5-methyl-2'-deoxycytidine in DNA + H(+) + S-adenosyl-L-homocysteine Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family.