LIN52 is a family of proteins of approximately 112 amino acids in length which is conserved from nematodes to humans. The proposed tertiary structure is of almost entirely alpha helix interrupted only by loops located at proline residues. Three sites in the protein sequence reveal two types of possible post-translation modification. A serine residue, at position 41, is a candidate for protein kinase C phosphorylation. Glycine residues at position 69 and 91 are probable sites for acetylation by covalent amide linkage of myristate via N-myristoyl transferase. LIN52 is differentially expressed in the trout retina between parr and smolt developmental stages (smoltification). It is likely to be a house-keeping protein [1]. LIN52 forms a complex (LINC) required for transcriptional activation of G2/M genes. The LINC core complex consists of at least five subunits including the chromatin-associated LIN-9 and RbAp48 proteins [2,3]. LINC associates with a large number of E2F-regulated promoters in quiescent cells [2]. Family members are required for spermatogenesis by repressing testis-specific gene expression [4].

1: Identification of a unique transcript down-regulated in the retina of rainbow trout (Oncorhynchus mykiss) at smoltification. Dann SG, Allison WT, Levin DB, Hawryshyn CW; Comp Biochem Physiol B Biochem Mol Biol. 2003;136:849-860. PMID:14662307

2: LINC, a human complex that is related to pRB-containing complexes in invertebrates regulates the expression of G2/M genes. Schmit F, Korenjak M, Mannefeld M, Schmitt K, Franke C, von Eyss B, Gagrica S, Hanel F, Brehm A, Gaubatz S; Cell Cycle. 2007;6:1903-1913. PMID:17671431

3: Evolutionarily conserved multisubunit RBL2/p130 and E2F4 protein complex represses human cell cycle-dependent genes in quiescence. Litovchick L, Sadasivam S, Florens L, Zhu X, Swanson SK, Velmurugan S, Chen R, Washburn MP, Liu XS, DeCaprio JA; Mol Cell. 2007;26:539-551. PMID:17531812

4: Wake-up-call, a lin-52 paralogue, and Always early, a lin-9 homologue physically interact, but have opposing functions in regulating testis-specific gene expression. Doggett K, Jiang J, Aleti G, White-Cooper H; Dev Biol. 2011;355:381-393. PMID:21570388