High impact information on HTA1

• Deletions at the N and C termini of yeast histones H2B2 and H2A1 do not obviously affect the cell's viability under normal growth conditions [1].
• First, the transcriptional defects in strains lacking these SNF genes are suppressed by a deletion of one of the two sets of genes encoding histones H2A and H2B, (hta1-htb1) delta [2].
• Regulation by histone gene dosage is dependent on a negative site in the HTA1-HTB1 promoter and the products of regulatory genes that act through this site [3].
• Using these mutant (hta1- and hta2-) strains we find that neither H2A gene has a unique essential function during any phase of the yeast life cycle, although strains homozygous for hta1- grow more slowly [4].
• However, AHC1 in high copy numbers suppresses the cold sensitivity caused by particular mutations in HTA1 (I. Pinto and F. Winston, personal communication), which encodes histone H2A (J. N. Hirschhorn et al., Mol. Cell. Biol. 15:1999-2009, 1995) [5].

Biological context of HTA1

• Tethered Hir1p also directed the periodic transcription of the HTA1 gene and repressed HTA1 transcription in response to two cell cycle regulatory signals [6].
• Specific mutations in HTA1, one of the two Saccharomyces cerevisiae genes encoding histone H2A, have been previously shown to cause chromosome segregation defects, including an increase in ploidy associated with altered pericentromeric chromatin structure, suggesting a role for histone H2A in kinetochore function [7].
• Here we show that a different mechanism of dosage compensation, at the level of gene copy number, can occur when HTA1-HTB1 is deleted [8].
• The HTA1-HTB1 locus causes suppression either when present on a high-copy-number plasmid or when mutant [9].
• Five recessive mutants with this phenotype were shown to contain altered regulatory genes because they had lost repression of HTA1 transcription which occurs upon inhibition of chromosome replication (D. E. Lycan, M. A. Osley, and L. Hereford, Mol. Cell. Biol. 7:614-621, 1987) [10].

Anatomical context of HTA1

• In this report, we demonstrate that either the HTA1 gene or the HTA2 gene, encoding the major H2As, can be completely replaced by disrupted genes in the polyploid, transcriptionally active macronucleus, indicating that neither of the two genes is essential [11].

Associations of HTA1 with chemical compounds

• This altered insertion pattern does not appear to be due to a bias caused by selecting canavanine resistant isolates in the different HTA1-HTB1 backgrounds [12].
• The cell cycle regulation sequence is responsible for the periodic accumulation and hydroxyurea sensitivity of the histone HTA1-HTB1 message [13].

Regulatory relationships of HTA1

• The results are consistent with the idea that the effects of the spt mutations on nucleosome assembly and/or stability activate repressors of HTA1 transcription [14].

Other interactions of HTA1

• We have identified a new class of mutations in the histone H2A-encoding gene HTA1 that causes transcriptional defects at the SNF/SWI-dependent gene SUC2 [15].
• Chromatin immunoprecipitation experiments indicate that, unlike wild-type Spt10p, the C388S protein does not bind to the promoter of the gene encoding histone H2A (HTA1) in vivo [16].

References