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Comments on Kemper, Kevin et al. (2013) International Worm Meeting "Heterochronic gene lin-46: protein expression and interaction with HBL-1." (0)
Overview
Kemper, Kevin, Vadla, Bhaskar, & Moss, Eric G. (2013). Heterochronic gene lin-46: protein expression and interaction with HBL-1 presented in International Worm Meeting. Unpublished information; cite only with author permission.
Alteration of the heterochronic pathway results in the abnormal timing of developmental events. lin-46 is a heterochronic gene discovered by its suppression of lin-28 and lin-14 precocious phenotypes. lin-46 mutations result in retarded hypodermal phenotypes, specifically reiteration of L2 seam cell divisions in the L3 and gaps in adult alae. LIN-46 protein resembles Gephyrin from mammals and MoeA from bacteria. Our studies of LIN-46 have identified both its expression pattern and interaction with another member of the heterochronic pathway. LIN-46 expression is restricted spatially and temporally, the basis being both transcriptional and post-translational. Using a GFP reporter we found LIN-46 expression in the cytoplasm and nucleus of lateral hypodermal seam cells, peaking around the time of the molts. Substituting other hypodermal promoters, such as col-10, showed similar restriction. Use of the pan-neuronal promoter rgef-1 indicates the temporal restriction is specific to the hypodermis. Preliminary qPCR data indicates periodic expression of the lin-46 mRNA also. lin-46 null mutants display a cold sensitivity. Temperature shift analysis specifies this cold sensitive period for all phenotypes to be two hours prior to the L2 molt. Genetic data places lin-46 in parallel with lin-28, potentially acting on common targets. LIN-28 has two mechanisms of action: supporting expression of HBL-1 and blocking let-7 accumulation. By qPCR, early let-7 levels in a lin-28(0); lin-46(0) mutant were unchanged from a lin-28(0) mutant alone, indicating no direct role for LIN-46 in let-7 regulation. A yeast two-hybrid screen using LIN-46 isolated a portion of the HBL-1 protein. The region isolated includes two C-terminal C2H2 zinc-fingers, a motif shown in related proteins to be involved in dimerization. Further analysis of the binding proved it to be specific. Injection of this fragment into wildtype animals caused a weakly retarded phenotype similar to lin-46(0). Injection into lin-46(0) animals caused a weakly precocious phenotype, indicating an interaction with other targets. These data indicate a role for LIN-46 in the post-translational regulation of HBL-1, possibly by inhibiting its interaction with other targets.
Affiliation:
- Molecular Biology, UMDNJ, Stratford, NJ.