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Tetrahymena H4 genes: structure, evolution and organization in macro- and micronuclei
Nucleic Acids Research
|February 24, 1984
Summary
Tetrahymena thermophila possesses two H4 histone genes, H4-I and H4-II, located on separate chromosomes. Evolutionary analysis reveals translation-level constraints on coding nucleotides, impacting gene evolution beyond protein function.
Area of Science:
- Molecular Biology
- Genetics
- Evolutionary Biology
Background:
- Tetrahymena thermophila has two distinct H4 histone genes: H4-I and H4-II.
- Histone genes are crucial for DNA packaging and gene regulation.
Purpose of the Study:
- To investigate the chromosomal organization of H4 histone genes in Tetrahymena thermophila.
- To explore the evolutionary pressures acting on H4 histone genes, particularly concerning non-protein-coding functions.
Main Methods:
- Southern blotting was employed to analyze DNA.
- Analysis of DNA from nullisomic strains identified gene locations.
- Comparative sequence analysis of H4-I and flanking regions against other organisms was performed.
Main Results:
- H4-I and H4-II genes are situated on different chromosomes.
- H4-II shows close linkage to an H3 gene.
- No DNA sequence rearrangements were detected between the micronucleus and macronucleus.
- Evolutionary constraints on coding nucleotides, independent of protein function, were identified.
Conclusions:
- The chromosomal organization of H4 histone genes in Tetrahymena is specific.
- Evolutionary pressures on H4 genes extend beyond protein sequence, influencing nucleotide selection at the translational level.