Regulatory subunit of casein kinase II/CK2. As part of the kinase complex regulates the basal catalytic activity of the alpha subunit a constitutively active serine/threonine-protein kinase that phosphorylates a large number of substrates containing acidic residues C-terminal to the phosphorylated serine or threonine (PubMed:11239457, PubMed:16818610). Participates in Wnt signaling (By similarity). {ECO:0000250|UniProtKB:P67871, ECO:0000269|PubMed:11239457, ECO:0000269|PubMed:16818610}. (Microbial infection) Upon infection with Epstein-Barr virus (EBV), the interaction with viral EBNA1 increases the association of CK2 with PML proteins, which increases PML phosphorylation by CK2, triggering the polyubiquitylation and degradation of PML (PubMed:20719947, PubMed:24216761). Seems to also suppress EBV reactivation by mediating ARK2N and JUN at the Z promoter which inhibits BZLF1 transcrition (PubMed:31341047). {ECO:0000269|PubMed:20719947, ECO:0000269|PubMed:24216761, ECO:0000269|PubMed:31341047}. This is the function of CSNK2B (casein kinase 2 beta, ENSG00000204435).