Has E2-dependent E3 ubiquitin-protein ligase activity (PubMed:12036302, PubMed:21423175). Responsible for ubiquitination of cAMP-dependent protein kinase type I and type II-alpha/beta regulatory subunits and for targeting them for proteasomal degradation. Essential for PKA-mediated long-term memory processes (PubMed:21423175). Through the ubiquitination of MFHAS1, positively regulates the TLR2 signaling pathway that leads to the activation of the downstream p38 and JNK MAP kinases and promotes the polarization of macrophages toward the pro- inflammatory M1 phenotype (PubMed:28471450). Plays a role in ciliogenesis by ubiquitinating OFD1 (PubMed:33934390). {ECO:0000269|PubMed:12036302, ECO:0000269|PubMed:21423175, ECO:0000269|PubMed:28471450, ECO:0000269|PubMed:33934390}. This is the function of ENSG00000198961 (PJA2, praja ring finger ubiquitin ligase 2).