TEG-1 CD2BP2 controls miRNA levels by regulating miRISC stability inC. elegansand human cells

Abstract

MiRNAs post-transcriptionally regulate gene expression by recruiting the miRNA-induced silencing complex (miRISC) to target mRNAs. However, the mechanisms by which miRISC components are maintained at appropriate levels for proper function are largely unknown. Here, we demonstrate that Caenorhabditis elegans TEG-1 regulates the stability of two miRISC effectors, VIG-1 and ALG-1, which in turn affects the abundance of miRNAs in various families. We demonstrate that TEG-1 physically interacts with VIG-1, and complexes with mature let-7 miRNA. Also, loss of teg-1 in vivo phenocopies heterochronic defects observed in let-7 mutants, suggesting the association of TEG-1 with miRISC is necessary for let-7 to function properly during development. Loss of TEG-1 function also affects the abundance and function of other microRNAs, suggesting that TEG-1's role is not specific to let-7. We further demonstrate that the human orthologs of TEG-1, VIG-1 and ALG-1 (CD2BP2, SERBP1/PAI-RBP1 and AGO2) are found in a complex in HeLa cells, and knockdown of CD2BP2 results in reduced miRNA levels; therefore, TEG-1's role in affecting miRNA levels and function is likely conserved. Together, these data demonstrate that TEG-1 CD2BP2 stabilizes miRISC and mature miRNAs, maintaining them at levels necessary to properly regulate target gene expression.

An ortholog of the Vasa intronic gene is required for small RNA-mediated translation repression in Chlamydomonas reinhardtii

“…S2). It was identified more than a decade ago as a component of the (mi)RISC in D. melanogaster, C. elegans, and human cells (24,25) but its actual mechanistic role(s) has not been elucidated. In C. elegans, VIG1 is required for let-7-mediated repression of a lacZ-lin-41 reporter, but not for (cleavage-mediated) RNAi (24).…”

“…Since the endogenous lin-41 transcript is translationally repressed by let-7 while associated with polyribosomes (13), it seems plausible that VIG1 is involved in this process. However, C. elegans vig1 mutants also show reduced levels of mature let-7 miRNAs, suggesting alternative (not mutually exclusive) VIG1 functions in miRISC loading and/or miRNA stability (25). Nonetheless, a growing body of evidence also supports the association of VIG/SERBP1 homologs with ribosomes.…”

“…VIG1 Copurifies with (mi)RISC Core Components. VIG/SERBP1 has been previously identified as a component of the (mi)RISC in D. melanogaster, C. elegans, and human cells (24,25). However, its role has remained somewhat enigmatic since its downregulation caused a slight (cleavage-mediated) RNAi defect in D. melanogaster and no obvious RNAi deficiency in C. elegans (24).…”

Redundant mechanisms regulating the proliferation vs. differentiation balance in the C. elegans germline

“…For example, enhancer screens were performed designed to identify tumorous enhancers of weak glp-1 gainof-function alleles, from which teg-1, teg-4 (tumorous enhancer of glp-1(gf)) and prp-17 (Yeast PRP17 related splicing factor) were identified (Mantina et al, 2009;Kerins et al, 2010;Wang et al, 2012). TEG-1 is homologous to CD2BP2, which has been implicated in U4/U6.U5 tri-snRNP formation (Wang et al, 2012(Wang et al, , 2017, TEG-4 is homologous to subunit 3 of SF3b (Mantina et al, 2009), and PRP-17 is homologous to the PRP17/CDC40 pre-mRNA splicing factor (Kerins et al, 2010). Other splicing factors have also been identified as being involved through other genetic screens or directly testing for potential involvement, including mog-1, mog-4, mog-5 (masculinization of germline), cyn-4/mog-6 and prp-19 Puoti and Kimble, 1999;Belfiore et al, 2004;Kerins et al, 2010;Gutnik et al, 2018).…”