A signal regulating mouse histone H4 mRNA levels in a mammalian cell cycle mutant and sequences controlling RNA 3' processing are both contained within the same 80-bp fragment
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Abstract:
Fragments from the 3' end of a mouse histone H4 gene, when introduced into transcription units controlled by the SV40 early promoter, yield correctly processed RNA with histone-specific 3' ends, both in monkey and mouse cell lines. The processed RNA is regulated in parallel with endogenous H4 mRNAs in 21-Tb cells, a temperature-sensitive mouse mastocytoma cell cycle mutant that is specifically blocked in G1 phase at the non-permissive temperature. Mutational analyses of the H4 gene fragment indicate that the minimal sequences for this regulation and for RNA 3' processing are both contained within the same 80 bp. This fragment contains two histone-specific, highly conserved sequence elements that are located at the 3' end of histone mRNA and in the adjacent spacer region, respectively. Our data suggest that the observed cell cycle regulation is achieved either at RNA 3' processing or at some later step involving the conserved 3'-terminal sequence element of mature histone mRNA.
Insights
Mouse histone H4 gene fragments show cell cycle regulation. Specific sequences control RNA processing and gene expression, impacting cell cycle progression.
Area of Science:
- Molecular Biology
- Gene Regulation
- Cell Biology
Background:
- Histone H4 is crucial for DNA packaging and cell cycle progression.
- Accurate RNA processing and 3' end formation are essential for gene expression.
- Cell cycle-specific regulation of histone gene expression is vital for DNA replication and cell division.
Purpose of the Study:
- To investigate the regulatory mechanisms controlling histone H4 gene expression.
- To identify the specific DNA sequences responsible for 3' end RNA processing and cell cycle regulation of histone H4.
- To elucidate how these sequences influence RNA processing and gene expression during the cell cycle.
Main Methods:
- Introduction of mouse histone H4 gene 3' end fragments into transcription units.
- Utilizing SV40 early promoter for gene expression control.
- Analysis in monkey and mouse cell lines, including a temperature-sensitive cell cycle mutant (21-Tb cells).
- Mutational analysis of the H4 gene fragment to pinpoint regulatory sequences.
Main Results:
- Correctly processed RNA with histone-specific 3' ends was produced from introduced gene fragments.
- The processed RNA exhibited cell cycle-dependent regulation, mirroring endogenous H4 mRNA levels in 21-Tb cells.
- A minimal 80 bp fragment contained sequences essential for both 3' end processing and cell cycle regulation.
- Two conserved sequence elements within this fragment were identified as critical for regulation and processing.
Conclusions:
- The 3' end of the mouse histone H4 gene contains regulatory elements controlling RNA processing and cell cycle-dependent expression.
- These regulatory mechanisms are linked to conserved sequence elements at the 3' end of histone mRNA and adjacent regions.
- Cell cycle regulation of histone H4 expression likely occurs at the RNA 3' processing stage or involves the mature mRNA's 3'-terminal sequence.