Structure and function analysis of LIN-14, a temporal regulator of postembryonic developmental events in Caenorhabditis elegans

During postembryonic development of Caenorhabditis elegans, the heterochronic gene lin-14 controls the timing of developmental events in diverse cell types. Three alternative lin-II transcripts are predicted to encode isoforms of a novel nuclear protein that differ in their amino-terminal domains. In this paper, we report that the alternative amino-terminal domains of LIN-14 are dispensable and that a carboxy-terminal region within exons 9 to 13 is necessary and sufficient for in vivo LIN-14 function. A transgene capable of expressing only one of the three alternative lin-14 gene products rescues a lin-14 null mutation and is developmentally regulated by lin-4. This shows that the deployment of alternative lin-II gene products is not critical for the ability of LIN-14 to regulate downstream genes in diverse cell types or for the in vivo regulation of LIN-14 level by lin-4, The carboxy-terminal region of LIN-14 contains an unusual expanded nuclear localization domain which is essential for LIN-14 function. These results support the view that LIN-14 controls developmental timing in C. elegans by regulating gene expression in the nucleus.