Associated component of the WMM complex, a complex that mediates N6-methyladenosine (m6A) methylation of RNAs, a modification that plays a role in the efficiency of mRNA splicing and RNA processing (PubMed:29507755). Acts as a key regulator of m6A methylation by promoting m6A methylation of mRNAs at the 3'-UTR (By similarity). Controls embryonic stem cells (ESCs) pluripotency via its role in m6A methylation (By similarity). In the WMM complex, anchors component of the MACOM subcomplex in the nucleus (By similarity). Also required for bridging WTAP to the RNA-binding component RBM15 (RBM15 or RBM15B) (By similarity). Component of the WMM complex, a N6-methyltransferase complex composed of a catalytic subcomplex, named MAC, and of an associated subcomplex, named MACOM (PubMed:29507755). The MAC subcomplex is composed of METTL3 and METTL14. The MACOM subcomplex is composed of WTAP, ZC3H13, CBLL1/HAKAI, VIRMA, and, in some cases of RBM15 (RBM15 or RBM15B) (PubMed:29507755). Also a component of a MACOM-like complex, named WTAP complex, composed of WTAP, ZC3H13, CBLL1/HAKAI, VIRMA, RBM15, BCLAF1 and THRAP3 (PubMed:24100041). Belongs to the ZC3H13 family.