Two steroid 15 alpha-hydroxylase genes and a homologous gene family in mice

Steroid 15 alpha-hydroxylase (P45015 alpha) activity is concomitant with the expression of two types of mRNA in the mouse liver. Two discrete genes, designated 15 alpha oh-1 and 15 alpha oh-2, that encode the two mRNAs were recovered from total genomic libraries of the inbred mouse strains 129/J and C57Bl/6J and identified by cDNA hybridization, restriction-site analysis and partial nucleotide sequence. Both genes are approx. 9 kb long and share significant homology, including flanking regions, over a region of at least 30 kb. The two distinct 15 alpha oh genes are members of a larger family of homologous genes and/or pseudogenes of unknown function. The most extensive sequence homology among family members in the 3' portion of the gene with progressively less homology toward the 5' end. The far 5' portions of 15 alpha oh-1 and 15 alpha oh-2 are very similar to one another but there is no observed homology with other genes of the family. The two 15 alpha oh genes and the homologous family have been localized to mouse chromosome 7 by somatic cell hybrid mapping. Analysis of a restriction fragment length polymorphism in recombinant inbred mice shows a close linkage of 15 alpha oh-1 and 15 alpha oh-2 with the Coh locus.     

Xenopus hsp 70 genes are constitutively expressed in injected oocytes.

Xenopus heat-shock genes are transiently heat-inducible in somatic cells, but they are also subject to a long-term developmental control in oogenesis and early embryogenesis. In order to understand whether different genes or different promoter elements are involved in the two types of control, several genomic clones coding for Xenopus heat-shock proteins, hsp 70 and hsp 30, were isolated, characterised and tested for expression in oocytes and COS cells. Three isolated hsp 70 genes are nearly identical in their promoter and mRNA leader sequences, indicating that there is only one type of hsp 70 gene. These promoters contain a consensus sequence element (CT-GAA--TTC-AG) upstream of the TATA-box, which is presumably required for their transient heat-inducibility. The two isolated hsp 30 genes show 5'-flanking sequences similar to each other, except that one of them shows a homology disruption precisely around the consensus sequence element. The same gene contains a frameshift mutation in the protein coding part and, since it cannot be expressed after introduction into oocytes or COS cells, it is probably a pseudogene. The other hsp 30 gene is strongly heat-inducible in injected oocytes or transfected COS cells. In contrast, the hsp 70 genes are strongly heat-inducible in COS cells, but their expression is highly efficient in injected oocytes at the normal temperature and is not increased during heat shock. This represents correct cell type-specific regulation of a cloned reintroduced gene, since the endogenous hsp 70 genes are constitutively activated during oogenesis, leading to the accumulation of stored hsp 70 mRNA in oocytes.     

Expression of heat shock genes during differentiation of mammalian osteoblasts and promyelocytic leukemia cells.

The progressive differentiation of both normal rat osteoblasts and HL-60 promyelocytic leukemia cells involves the sequential expression of specific genes encoding proteins that are characteristic of their respective developing cellular phenotypes. In addition to the selective expression of various phenotype marker genes, several members of the heat shock gene family exhibit differential expression throughout the developmental sequence of these two cell types. As determined by steady state mRNA levels, in both osteoblasts and HL-60 cells expression of hsp27, hsp60, hsp70, hsp89 alpha, and hsp89 beta may be associated with the modifications in gene expression and cellular architecture that occur during differentiation. In both differentiation systems, the expression of hsp27 mRNA shows a 2.5-fold increase with the down-regulation of proliferation while hsp60 mRNA levels are maximal during active proliferation and subsequently decline post-proliferatively. mRNA expression of two members of the hsp90 family decreases with the shutdown of proliferation, with a parallel relationship between hsp89 alpha mRNA levels and proliferation in osteoblasts and a delay in down-regulation of hsp89 alpha mRNA levels in HL-60 cells and of hsp89 beta mRNA in both systems. Hsp70 mRNA rapidly increases, almost twofold, as proliferation decreases in HL-60 cells but during osteoblast growth and differentiation was only minimally detectable and showed no significant changes. Although the presence of the various hsp mRNA species is maintained at some level throughout the developmental sequence of both osteoblasts and HL-60 cells, changes in the extent to which the heat shock genes are expressed occur primarily in association with the decline of proliferative activity. The observed differences in patterns of expression for the various heat shock genes are consistent with involvement in mediating a series of regulatory events functionally related to the control of both cell growth and differentiation.     

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.     

Expression of endogenous and microinjected hsp 30 genes in early Xenopus laevis embryos

In the present study, we have examined the regulation of expression of a newly isolated member of the hsp 30 gene family, hsp 30C. Using RT-PCR, we found that this gene was first heat-inducible at the tailbud stage of development. We also examined the expression of two microinjected modified hsp 30C gene constructs in Xenopus embryos. One of the constructs had 404 bp of hsp 30C 5′-flanking region, whereas the other had 3.6 kb. Both gene constructs had 1 kb of 3′-flanking region. RT-PCR assays were employed to detect the expression of these microinjected genes. The presence of extensive 5′- and 3′-flanking regions of the hsp 30C gene did not confer proper developmental regulation, since heat-inducible expression of both of the microinjected constructs was detectable at the midblastula stage. The premature expression of the microinjected hsp 30 gene was not a result of high plasmid copy number or the presence of plasmid DNA sequences. These results suggest that the microinjected genes contain all the cis-acting DNA sequences required for correct heat-inducible regulation but do not contain the elements required for the proper regulation of hsp 30 gene expression during development. It is possible that regulatory elements controlling the developmental expression of the hsp30 genes may reside upstream or downstream of the entire cluster. © 1993Wiley-Liss, Inc.     

Phylogenetic analyses suggest lateral gene transfer from the mitochondrion to the apicoplast

The genomes of the three temperate bacteriophages contained in the chromosome of Staphylococcus aureus 8325 have been extracted from the sequence database and analyzed. phi 11, phi 12 and phi 13 are members of the same lytic group but different serogroups and consequently co-habitate the same host cell. Their genomes are approximately 42 kb to 45 kb and contain about 90 ORFs of at least 50 codons. Of these, about 50 have similarities to known genes or to genes of other staphylococcal phages. Each of the phages clusters within a homology group that share large regions of sequence identity while intergroup homology is comparatively low. The arrangement of genes on the chromosomes of the three phages is similar and consistent with current modular theory of phage gene organization. The replicated genomes appear to be packaged by different mechanisms. Phage phi 11 and phi 12 have been found to contain sequences consistent with pac-site phages while phi 13 has sequences consistent with cos-site phages. The attBsite for phi 11 is located in an intergenic region of the S. aureus chromosome while phi 12 and phi 13 integrate into specific genes. The phi 12 att-site is within an unknown gene, but the phi 13 att-site is within the beta-toxin gene. In contrast to the other two phages, phi 13 also introduces the staphylokinase gene (sak) and a second gene related to expression of fib.     

Cloning and nucleotide sequencing of three heat shock protein genes (hsp90, hsc70, and hsp19.5) from the diamondback moth, Plutella xylostella (L.) and their expression in relation to developmental stage and temperature

Heat shock protein genes, hsp90, hsc70, and hsp19.5, were cloned and sequenced from the diamondback moth, Plutella xylostella (L.) by RT-PCR and RACE method. The cDNA sequence analysis of hsp90 and hsp19.5 revealed open reading frames (ORFs) of 2,151 and 522 bp in length, which encode proteins with calculated molecular weights of 82.4 and 19.5 kDa, respectively. Analysis of cDNA from hsc70 revealed an ORF of 1,878 bp coding a protein with a calculated molecular weight of 69.3 kDa. Furthermore, the analysis of genomic DNA from hsc70 confirmed the presence of introns while no introns were apparent in hsp90 and hsp19.5. Southern blot analysis suggested the presence of multiple copies of each gene family in the DBM genome. Detectable expression of hsp19.5 was observed at the pupal stage while expression of hsp90 and hsc70 was detected at both pupal and adult stages. At adult stage, females showed a higher expression of hsp90 and hsc70 than males. An increased expression was observed in all three genes after exposure to a high temperature in both sexes. These results suggest that in addition to a heat shock response, these HSP genes might be involved in other functions during the course of development in DBM.