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Deactivation of gene expression upon the onset of development in dictyostelium discoideum
C K Singleton1, C E McPherson, S S Manning
1Department of Molecular Biology, Vanderbilt University, Nashville, TN 37235.
Abstract:
Several genes that are deactivated upon the initiation of development of Dictyostelium discoideum have been identified by differential screening of various cDNA libraries. These genes have in common a decrease in the steady-state levels of their corresponding mRNAs as development proceeds. When development was carried out in the absence of protein synthesis by inhibition with cycloheximide, the decrease in mRNA levels for most genes (V genes) was normal or slightly accelerated. However, for about 5% of the genes (H genes), cycloheximide caused an apparent induction of expression, as revealed by a slight or dramatic increase in mRNA levels instead of the normal decrease. This effect was due to inhibition of protein synthesis and not to cycloheximide per se. The induction was found to be due to an enhancement of the transcription rate; normal rates of transcription for the H genes were dependent upon continued protein synthesis during vegetative growth and during development. Thus, two general regulatory classes exist for deactivation of gene expression upon initiation of development, one dependent and one independent of protein synthesis. Models concerning the control of expression of these two classes of genes are discussed here. Analysis of expression of these genes in mutant strains that are aggregation-deficient has also been performed, and the results lead to subdivisions of the classes.
Insights
Researchers identified two gene expression classes during Dictyostelium discoideum development. One class
Area of Science:
- Molecular Biology
- Developmental Biology
- Gene Regulation
Background:
- Dictyostelium discoideum development involves complex gene regulation.
- Many genes are deactivated as development initiates.
- Understanding these regulatory mechanisms is crucial for developmental biology.
Purpose of the Study:
- To identify genes deactivated during Dictyostelium discoideum development.
- To classify these genes based on their response to inhibited protein synthesis.
- To elucidate regulatory mechanisms controlling gene expression during development.
Main Methods:
- Differential screening of cDNA libraries to identify deactivated genes.
- Inhibition of protein synthesis using cycloheximide during development.
- Analysis of mRNA levels and transcription rates for identified gene classes.
- Study of gene expression in aggregation-deficient mutant strains.
Main Results:
- Identified genes with decreasing mRNA levels during development.
- Discovered two classes: V genes (normal decrease with cycloheximide) and H genes (apparent induction).
- H gene induction is due to enhanced transcription dependent on protein synthesis.
- Aggregation-deficient mutants revealed subdivisions within these classes.
Conclusions:
- Two distinct regulatory classes of gene deactivation exist during Dictyostelium discoideum development: protein synthesis-dependent and independent.
- Protein synthesis is essential for normal transcription rates of H genes.
- Further subdivisions of regulatory classes were identified using mutant strains.