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Effect of protein synthesis inhibition on gene expression during early development of Dictyostelium discoideum
C K Singleton1, S S Manning, Y Feng
1Department of Molecular Biology, Vanderbilt University, Nashville, Tennessee 37235.
Abstract:
Several genes which are deactivated on the initiation of development of Dictyostelium discoideum were identified by differential screening of various cDNA libraries. These genes have in common a decrease in the steady-state levels of their corresponding mRNAs on the onset of development and 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. For about 5% of the genes (H genes), however, 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 on continued protein synthesis during vegetative growth and development. Thus, two general regulatory classes exist for deactivation of gene expression on initiation of development, one of which is dependent on and one of which is independent of protein synthesis. Analysis of expression of these genes in mutant strains which are aggregation deficient allowed the classes to be subdivided further. Taken together, these characterizations allow several distinct regulatory mechanisms to be identified that are involved in the deactivation of gene expression on the onset of development in D. discoideum.
Insights
Gene expression in Dictyostelium discoideum development is deactivated through two main pathways. Some genes require protein synthesis for deactivation, while others do not, revealing distinct regulatory mechanisms.
Area of Science:
- Molecular Biology
- Developmental Biology
- Cellular Biology
Background:
- Gene expression regulation is crucial for cellular differentiation and development.
- Dictyostelium discoideum serves as a model organism for studying multicellular development and gene regulation.
Purpose of the Study:
- To identify and characterize genes deactivated during Dictyostelium discoideum development.
- To elucidate the regulatory mechanisms underlying gene deactivation, particularly the role of protein synthesis.
Main Methods:
- Differential screening of cDNA libraries to identify differentially expressed genes.
- Inhibition of protein synthesis using cycloheximide to study mRNA level changes.
- Analysis of gene expression in aggregation-deficient mutant strains.
Main Results:
- Identified genes with decreased mRNA levels during development (V genes and H genes).
- Demonstrated that most gene deactivation (V genes) is independent of protein synthesis.
- Discovered that a subset of genes (H genes) requires ongoing protein synthesis for normal deactivation, with inhibition leading to apparent induction via enhanced transcription.
Conclusions:
- Two distinct classes of gene deactivation exist: protein synthesis-dependent and protein synthesis-independent.
- Protein synthesis plays a regulatory role in the deactivation of specific genes during development.
- Further subdivision of these classes in mutant strains suggests complex regulatory networks controlling gene expression onset in Dictyostelium discoideum development.