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Changes in the H-1 histone complement during myogenesis. II. Regulation by differential coupling of H-1 variant mRNA
Abstract:
We have shown that changes in proportions of the four chicken H-1's during in vitro myogenesis are primarily the result of differential coupling of their synthesis to DNA replication (see the previous paper). We show here that the four major chicken H-1's are encoded by distinct mRNAs which specify primary amino acid sequence variants. Accumulation of the H-1-variant mRNAs is coupled to DNA replication to different extents. The level of mRNA encoding H-1c (the H-1 variant that increases relative to the other H-1's in nondividing muscle cells) is completely uncoupled. In contrast, the level of mRNAs encoding H-1's a, b, and d (which have levels that decrease in nondividing muscle cells) are more tightly coupled. Polyadenylation is not involved in uncoupling H-1c mRNA accumulation from DNA replication.
Insights
Changes in chicken H-1 protein levels during muscle development are due to distinct messenger RNA (mRNA) accumulations. H-1c mRNA levels are uncoupled from DNA replication, unlike other H-1 variants.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Chicken H-1 proteins are histone variants crucial for chromatin structure.
- Previous work indicated differential synthesis of H-1 variants during myogenesis is linked to DNA replication.
Purpose of the Study:
- To investigate the molecular mechanisms underlying differential H-1 variant accumulation during chicken myogenesis.
- To determine if distinct mRNAs encode the four major chicken H-1 variants and how their accumulation relates to DNA replication.
Main Methods:
- Analysis of mRNA populations encoding chicken H-1 variants using molecular biology techniques.
- Quantification of mRNA levels in relation to DNA replication during in vitro myogenesis.
- Investigation of the role of polyadenylation in mRNA accumulation control.
Main Results:
- The four major chicken H-1 variants are encoded by distinct mRNAs specifying different primary amino acid sequences.
- Accumulation of H-1 variant mRNAs is differentially coupled to DNA replication.
- mRNA for H-1c, which increases in non-dividing muscle cells, is completely uncoupled from DNA replication.
- mRNAs for H-1 variants a, b, and d, which decrease in non-dividing muscle cells, are more tightly coupled to DNA replication.
- Polyadenylation does not play a role in the uncoupling of H-1c mRNA accumulation.
Conclusions:
- Differential mRNA synthesis and distinct regulatory mechanisms controlling mRNA accumulation, rather than post-transcriptional modification like polyadenylation, explain the varying proportions of chicken H-1 variants during myogenesis.
- The uncoupling of H-1c mRNA from DNA replication allows its increased accumulation in differentiating, non-dividing muscle cells.