8798156

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The mec-3 gene of Caenorhabditis elegans encodes a homeodomain protein and is expressed in one of two cells upon asymmetric cell division. As a result of asymmetric mec-3 expression, the two sister cells express different fates, so mec-3 is a likely target for the machinery that mediates asymmetric cell division. The unc-86 gene encodes a homeodomain protein of the POU family, which activates mec-3 by binding to its promoter. The ten mec-3-expressing cells are a subset of the anterior daughters of UNC-86-containing cells. Posterior daughters of UNC-86-containing cells do not express mec-3, even though the UNC-86 protein is distributed into both daughter cells. Lineages that express the unc-86 and mec-3 genes can be grouped into two types: in Type I lineages, UNC-86 protein is first made in the immediate parent of the terminal mec-3-expressing cell, while in Type II lineages, UNC-86 is first made in the grandparent of the terminal mec-3-expressing cell. The purpose of experiments presented here is to understand the relationship between the mec-3 expression patterns in each type of lineage, and to determine the fundamental activity pattern of the mec-3 promoter. We find that in the Type I V5.pa lineage, mec-3-lacZ is first synthesized in the terminal PVDR neuron, one cell division after unc-86 is expressed. mec-3 expression in PVDR can occur by transcriptional regulation alone; segregation of the mec-3 RNA or protein is not required to explain the asymmetric expression of mec-3. In the Type II Q lineage, the mec-3 promoter activity can be detected in the immediate anterior daughter of the first unc-86-expressing cell, but when this cell divides, mec-3 is expressed in only one of its daughters at later times. It seems likely that, in the short-lived immediate anterior daughter cell in Type II lineages, mec-3 product does not accumulate to levels that can influence subsequent events. Our results suggest that the mec-3 promoter is activated in all anterior daughters of unc-86-expressing cells.

eng

IM

MEDLINE

0925-4773

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NLM

165-81

pubmed-meshheading:8798156-Animals, pubmed-meshheading:8798156-Animals, Genetically Modified, pubmed-meshheading:8798156-Apoptosis, pubmed-meshheading:8798156-Caenorhabditis elegans, pubmed-meshheading:8798156-Caenorhabditis elegans Proteins, pubmed-meshheading:8798156-Cell Division, pubmed-meshheading:8798156-Cell Lineage, pubmed-meshheading:8798156-Cell Polarity, pubmed-meshheading:8798156-Embryo, Nonmammalian, pubmed-meshheading:8798156-Gene Expression Regulation, Developmental, pubmed-meshheading:8798156-Heat-Shock Proteins, pubmed-meshheading:8798156-Helminth Proteins, pubmed-meshheading:8798156-Homeodomain Proteins, pubmed-meshheading:8798156-LIM-Homeodomain Proteins, pubmed-meshheading:8798156-Nerve Tissue Proteins, pubmed-meshheading:8798156-Neurons, pubmed-meshheading:8798156-POU Domain Factors, pubmed-meshheading:8798156-Promoter Regions, Genetic, pubmed-meshheading:8798156-Recombinant Fusion Proteins, pubmed-meshheading:8798156-Transcription Factors

Activation of the mec-3 promoter in two classes of stereotyped lineages in Caenorhabditis elegans.

Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't