A human histone H2B.1 variant gene, located on chromosome 1, utilizes alternative 3' end processing

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Histone genes are crucial for DNA packaging and replication.
• The H2B-GL105 gene was previously identified as encoding a replication-independent mRNA.

Purpose of the Study:

• To investigate the cell cycle regulation of the H2B-GL105 gene.
• To characterize the alternative mRNA transcripts produced by H2B-GL105.
• To determine the chromosomal location and genomic context of H2B-GL105.

Main Methods:

• Cloning of the H2B-GL105 gene.
• Analysis of mRNA expression during the HeLa S3 cell cycle.
• Chromosomal in situ hybridization and somatic cell hybrid analysis.
• Identification of gene regulatory elements.

Main Results:

• H2B-GL105 expresses both a 500 nt cell cycle-dependent mRNA and a 2300 nt constitutively expressed mRNA.
• The cell cycle-dependent mRNA has a standard histone mRNA 3' end, while the constitutive mRNA has a polyadenylated 1798 nt trailer.
• The H2B-GL105 gene is located on chromosome 1q21-1q23 and is part of an H2A/H2B gene pair with a bidirectional promoter.
• Alternative 3' end processing is implicated in regulating histone mRNA levels.

Conclusions:

• A single histone gene can produce both cell cycle-regulated and constitutively expressed mRNAs.
• Alternative 3' end processing is a significant mechanism for controlling histone mRNA levels.
• This regulatory mechanism enhances cellular control over histone protein synthesis during the cell cycle and differentiation.