This family contains several eukaryotic sequences such as CDK5RAP3 (also known as C53 or LZAP) which serves as a probable tumour suppressor. Initially identified as a CDK5R1 interactor controlling cell proliferation [1, 2]. It negatively regulates NF-kappa-B-mediated gene transcription through the control of RELA phosphorylation [3, 4]. It also regulates mitotic G2/M transition checkpoint and mitotic G2 DNA damage checkpoint [5, 6]. It has been shown to bind Wip1 and stimulates its phosphatase activity [7].

1: A novel gene IC53 stimulates ECV304 cell proliferation and is upregulated in failing heart. Chen J, Liu B, Liu Y, Han Y, Yu H, Zhang Y, Lu L, Zhen Y, Hui R; Biochem Biophys Res Commun. 2002;294:161-166. PMID:12054757

2: Cloning and characterization of human IC53-2, a novel CDK5 activator binding protein. Xie YH, He XH, Tang YT, Li JJ, Pan ZM, Qin WX, Wan DF, Gu JR; Cell Res. 2003;13:83-91. PMID:12737517

3: LZAP, a putative tumor suppressor, selectively inhibits NF-kappaB. Wang J, An H, Mayo MW, Baldwin AS, Yarbrough WG; Cancer Cell. 2007;12:239-251. PMID:17785205

4: A novel C53/LZAP-interacting protein regulates stability of C53/LZAP and DDRGK domain-containing Protein 1 (DDRGK1) and modulates NF-kappaB signaling. Wu J, Lei G, Mei M, Tang Y, Li H; J Biol Chem. 2010;285:15126-15136. PMID:20228063

5: Cdk5 activator-binding protein C53 regulates apoptosis induced by genotoxic stress via modulating the G2/M DNA damage checkpoint. Jiang H, Luo S, Li H; J Biol Chem. 2005;280:20651-20659. PMID:15790566

6: Tumor suppressor protein C53 antagonizes checkpoint kinases to promote cyclin-dependent kinase 1 activation. Jiang H, Wu J, He C, Yang W, Li H; Cell Res. 2009;19:458-468. PMID:19223857

7: LZAP is a novel Wip1 binding partner and positive regulator of its phosphatase activity in vitro. Wamsley JJ, Issaeva N, An H, Lu X, Donehower LA, Yarbrough WG; Cell Cycle. 2017;16:213-223. PMID:28027003