Mutations in aurora prevent centrosome separation leading to the formation of monopolar spindles

The response of cells to a heat shock or other stresses is the activation of a small number of genes which were previously inactive or transcribed at low levels. This response has been observed in a wide variety of bacterial, plant, and animal species. Evidence is accumulating that at least some of the proteins found in diverse species are similar, indicating a conservation of the response and the proteins in evolution. In a number of organisms a strong positive correlation has been found between the presence of heat shock proteins and ability of the organism to withstand thermal stress. This review attempts to assess the available data concerning the homology of proteins in different species, the localization of the proteins in cells, and the relationship between heat shock proteins and thermoresistance.

The heat shock response.

Studies of cloned sequences from four Drosophila heat shock loci.

High-sensitivity S1 mapping with single-stranded [32P]DNA probes synthesized from bacteriophage M13mp templates.

Putative function of Drosophila melanogaster heat shock proteins in the nucleoskeleton.

Drosophila melanogaster tissues carrying a third chromosome with the deletion Df(3R)KarD2 make a 40,000-dalton (Dal) heat shock protein not made by wild type. The unusual polypeptide was inducible in every tissue examined. Tryptic peptide fingerprints showed it to include part of the 70,000-Dal major heat shock protein. Mapping experiments placed the mutation responsible for the 40,000-Dal protein at or close to the karD2 deletion. One break point of the deletion is in subdivision 87A, close to or at a heat shock locus that codes for the 70,000-Dal protein. The results are consistent with the possibility that this break point is within a gene for the 70,000-Dal protein, leaving only the initial portion of its coding sequence. This would specify the direction of transcription of the mutant gene as proximal to distal on the normal chromosome. The 87A heat shock locus should contain at least two genes for the 70,000-Dal protein, because embryos homozygous for the karD2 deletion and lacking the heat shock locus at 87C, which also codes for the 70,000-Dal protein, nevertheless produced both the 40,000-Dal and the 70,000-Dal proteins upon temperature elevation. Using the presence of the 40,000-Dal protein to monitor chromosome segregation, we found that embryos homozygous for deletions of the heat shock puff site at 93D exhibited a normal electrophoretic pattern of heat shock proteins.

R. Caizzi

Papers

Mutation generating a fragment of the major heat shock-inducible polypeptide in Drosophila melanogaster