Analysis of the cytosolic hsp70 gene family inZea mays

In this study we have analysed the multigene family coding for the cytoplasmic heat shock 70 kDa proteins (hsp70) inZea mays. Fully degenerate primers were used in a polymerase chain reaction (PCR) to amplify selected regions of the hsp70 genes. Sequence and Southern blot analysis reveals that at least three highly conserved genes exist in maize. In addition, amplification reveals the presence of a conserved intron in all genes examined. Expression analysis shows that the hsp70 genes studied represent members of the inducible and constitutive families. The results obtained may indicate that there are subfamilies of cytoplasmic hsp70 genes expressed in higher plants.     

A human gene family with sequence homology to Drosophila melanogaster Hsp70 heat shock genes

A growing literature describes the structure and regulation of prokaryotic and eukaryotic heat shock genes. We here report the isolation of several members of a human heat shock protein 70 (hsp 70) multigene family which contains at least 10 different genes and/or pseudogenes exhibiting sequence homology to the hsp70 gene of Drosophila melanogaster. Eight nonoverlapping recombinant lambda phages from a lambda-Charon4A human genomic library were studied by restriction mapping. One lambda clone was sequenced and characterized as a hsp70 pseudogene inserted into a rearranged human HindIII 1.9-kilobase repeated DNA sequence. This pseudogene is probably located on the X chromosome. Its predicted amino acid sequence shows extensive homology to those of Drosophila hsp70, trout hsp70, Xenopus hsp70, yeast hsp70, and some homology to the heat-inducible dnaK gene product of Escherichia coli. Amino acid homology is clustered, suggesting evolutionary conservation of domains critical to the function of this protein in both prokaryotic and eukaryotic cells.     

Mutations in cognate genes of Saccharomyces cerevisiae hsp70 result in reduced growth rates at low temperatures.

Expression of two Saccharomyces cerevisiae genes (YG101 and YG103) that are related to the gene encoding inducible 70K protein (hsp70) is repressed upon heat shock. Mutations of the two genes were constructed in vitro and substituted into the yeast genome in place of the wild-type alleles. No phenotypic effect of single mutations of either gene was detected. However, cells containing both YG101 and YG103 mutations showed altered growth properties; double-mutation cells possess an optimal growth temperature of 37 degrees C rather than 30 degrees C and grow increasingly poorly as the temperature is lowered. Mutations of two other members of this hsp70-related multigene family, YG100 and YG102, have been analyzed (E. A. Craig and K. Jacobsen, Cell 38:841-849, 1984). Cells containing both YG100 and YG102 mutations cannot form colonies at 37 degrees C. Fusions between the YG101 and YG102 promoter regions and the YG100 and YG101 structural genes, respectively, were constructed. The YG101 promoter-YG100 structural gene fusion was not able to restore normal growth properties to the yg101- yg103- mutant. Also, yg100- yg102- cells containing the YG102 promoter-YG101 structural gene fusion were unable to grow at 37 degrees C. Failure of the protein products of related genes to rescue the relative cold sensitivity of growth suggests that members of the hsp70 multigene family are functionally distinct.     

A high degree of DNA strain polymorphism associated with the major heat shock gene in Caenorhabditis elegans

Summary We have searched for sequence variation between the Bristol and Bergerac strains of C. elegans in regions flanking three members of the 70 kilodalton (kd) heat shock peptide (hsp) gene family. No sequence variation was detected in 40 kb of DNA flanking two 70 kd hsp genes which are not stimulated by heat shock. In contrast, analysis of DNA flanking the heat shock inducible 70 kd hsp gene showed an unusually high amount of sequence variation between the two strains. Isolation and restriction map analysis of this gene from both strains revealed that the 5 and 3 flanking regions have diverged by 8.1 and 7.0% in nucleotide sequence, respectively. We have shown that these alterations are not due to large DNA rearrangements and conclude that the majority of sequence difference is the result of point mutations. Our results suggest that the heat shock inducible 70 kd hsp gene region accumulates mutations at a rate 10 to 20 fold higher than other regions of the genome. We propose that the anomalously high accumulation of mutational events is a direct consequence of the special status of the 70 kd hsp gene and its surrounding chromatin domain in the germline of C. elegans.     

Structure, organization, and expression of the 16-kDa heat shock gene family of Caenorhabditis elegans

Exposure of the nematode Caenorhabditis elegans to a heat shock results in the induction of a number of genes not normally expressed in the animals under normal growth conditions. Among these are a family of genes encoding 16 kDa heat shock proteins (hsp16s). The major hsp16 genes have been cloned and characterized, and found to reside at two clusters in the C. elegans genome. One cluster contains two distinct genes, hsp16-1 and hsp16-48, arranged in divergent orientations separated by only 348 base pairs (bp). An identical pair, duplicated and inverted with respect to the first pair, is located 415 bp away. This cluster, located on chromosome V, therefore contains four genes as two identical pairs within less than 4 kilobases of DNA, and the pairs form the arms of a large inverted repeat. A second pair of genes, hsp16-2 and hsp16-41, constitutes a second hsp16 locus with an organization very similar to that of the hsp16-1/48 locus, except that it is not duplicated. Comparisons of the derived amino acid sequences show that hsp16-1 and hsp16-2 form a closely related pair, as do hsp16-41 and hsp16-48. These hsps show extensive sequence identity with the small hsps of Drosophila, as well as with mammalian alpha-crystallins. The coding region of each gene is interrupted by a single intron of approximately 50 bp, in a position homologous to that of the first intron in mouse alpha-crystallin gene.(ABSTRACT TRUNCATED AT 250 WORDS)