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Differential expression of two clusters of mouse histone genes
Abstract:
The mouse histone mRNAs coded for by three different cloned DNA fragments have been characterized. Two of these cloned DNA fragments, MM221 and MM291, located on chromosome 13, code for H3, H2b and H2a histone mRNAs, which are expressed at low levels in cultured mouse cells and fetal mice. The other DNA fragment, MM614, located on chromosome 3, codes for an H3 and an H2a mRNA, which are expressed at high levels in these cells. The mRNAs for each histone protein share common coding region sequences, while the untranslated regions of all the genes have diverged significantly, as judged by S1 nuclease mapping. Amino acid substitutions in some H3, H2a and H2b proteins are detected as internal cleavages in the S1 nuclease maps. All of these genes code for replication variant histone mRNAs, which are regulated in parallel with DNA synthesis.
Insights
Mouse histone genes on different chromosomes show varied expression levels and divergent untranslated regions. These replication variant histone mRNAs are regulated alongside DNA synthesis.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Histones are crucial proteins for DNA packaging and gene regulation.
- Understanding histone gene expression is vital for cellular processes like DNA replication and cell division.
Purpose of the Study:
- To characterize mouse histone mRNAs from different DNA fragments.
- To investigate the expression levels and sequence divergence of histone genes.
- To determine the regulation patterns of replication variant histone mRNAs.
Main Methods:
- Cloning and characterization of mouse histone DNA fragments.
- Analysis of histone mRNA expression in cultured mouse cells and fetal mice.
- S1 nuclease mapping to assess mRNA sequence divergence and detect amino acid substitutions.
Main Results:
- Identified three mouse histone DNA fragments (MM221, MM291, MM614) on chromosomes 3 and 13.
- Two fragments (MM221, MM291) code for low-expressed H3, H2b, and H2a histone mRNAs.
- One fragment (MM614) codes for highly expressed H3 and H2a histone mRNAs.
- Common coding regions but divergent untranslated regions observed across histone genes.
- S1 nuclease mapping revealed amino acid substitutions in H3, H2a, and H2b proteins.
Conclusions:
- Mouse histone genes exhibit differential expression patterns linked to their chromosomal location.
- Divergence in untranslated regions suggests distinct regulatory mechanisms for histone gene variants.
- Replication variant histone mRNAs are coordinately regulated with DNA synthesis, impacting cell proliferation.