Biomedical subjects

E Hickey

Publications and source records attributed to E Hickey.

8 recordsLinked to original sources

PubMed2001

mtDna and the islands of the North Atlantic: estimating the proportions of Norse and Gaelic ancestry.

A total of 1,664 new mtDNA control-region sequences were analyzed in order to estimate Gaelic and Scandinavian matrilineal ancestry in the populations of Iceland, Orkney, the Western Isles, and the Isle of Skye and to investigate other aspects of their genetic history. A relative excess of private lineages in the Icelanders is indicative of isolation, whereas the scarcity of private lineages in Scottish island populations may be explained by recent gene flow and population decline. Differences in the frequencies of lineage clusters are observed between the Scandinavian and the Gaelic source mtDNA pools, and, on a continent-wide basis, such differences between populations seem to be associated with geography. A multidimensional scaling analysis of genetic distances, based on mtDNA lineage-cluster frequencies, groups the North Atlantic islanders with the Gaelic and the Scandinavian populations, whereas populations from the central, southern, and Baltic regions of Europe are arranged in clusters in broad agreement with their geographic locations. This pattern is highly significant, according to a Mantel correlation between genetic and geographic distances (r=.716). Admixture analyses indicate that the ancestral contributions of mtDNA lineages from Scandinavia to the populations of Iceland, Orkney, the Western Isles, and the Isle of Skye are 37.5%, 35.5%, 11.5%, and 12.5%, respectively.

Atlantic Islands↗

PubMed1992

Human HSP27 is phosphorylated at serines 78 and 82 by heat shock and mitogen-activated kinases that recognize the same amino acid motif as S6 kinase II.

The intracellular concentration of the 27-kDa mammalian heat shock protein, HSP27, increases several-fold after heat and other metabolic stresses and is closely associated with the acquisition of thermotolerance. Posttranslational modifications may also affect the function of HSP27. Heat shock of HeLa cell cultures, or treatment with arsenite, phorbol ester, or tumor necrosis factor, caused a rapid phosphorylation of preexisting HSP27 and the appearance of three phosphorylated isoforms, HSP27 B, C, and D. Digestion with trypsin and fractionation of the peptides by reverse phase high performance liquid chromatography revealed three 32P-labeled phosphopeptides. Microsequence analysis identified peak I as Ala76-Leu77-Ser78-Arg79 and peak II as Gln80-Leu81-Ser82-Ser83-Gly84-Val85- Ser86-Glu87-Ile88-Arg89; peak III contained the undigested peptide pair Ala76-Arg89. Ser82 was the major site and Ser78 the minor site of phosphorylation. Mutant proteins with Ser78 or Ser82 altered to glycine or Ser78-Ser82 double mutants were phosphorylated to reduced extents in vivo after heat or arsenite treatment. Ser78 and Ser82 (and Ser15) occur in the sequence motif RXXS, which is recognized by ribosomal protein S6 kinase II. Mitogenic stimulation of serum-deprived, Go-arrested Chinese hamster cells with serum, thrombin, or fibroblast growth factor also stimulated phosphorylation of HSP27 Ser78 and Ser82, and mitogenic stimulation and heat shock activated protein kinase activities that phosphorylated HSP27 and protein S6 in vitro. These results suggest that HSP27 may exert phosphorylation-activated functions linked with growth signaling pathways in unstressed cells. A homeostatic function at this level could protect cells from adverse effects of signal transduction systems which may be activated inappropriately during stress.

Amino Acid Sequence↗

PubMed1992

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.

Animals↗

PubMed1991

Stress response protein (srp-27) determination in primary human breast carcinomas: clinical, histologic, and prognostic correlations.

Expression of an estrogen-regulated protein known as the 27,000-d heat-shock or stress-response protein (srp-27) was evaluated in human breast carcinomas and established breast cancer cell lines. Results obtained by Northern and Western blot analyses and immunohistochemical methods were concordant. Immunohistochemical assessment of srp-27 expression in 300 breast carcinomas (with median patient follow-up of 8 years) was performed. Twenty-six percent of lymph node-negative and 45% of lymph node-positive tumors were overexpressors. Univariate analysis demonstrated significant correlations between srp-27 overexpression and estrogen receptor (ER) content, pS2 protein expression, nodal metastases, advanced T stage, lymphatic/vascular invasion, and a shorter disease-free survival period (but not a shorter overall survival) for the study population as a whole. Regression tree analysis showed that srp-27 expression was an independent prognostic indicator for disease-free survival only in patients with one to three positive lymph nodes. The Cox proportional hazards model confirmed the independent prognostic significance of nodal involvement, T stage, and ER content but failed to recognize srp-27 overexpression as a significant independent parameter predictive of patient outcome in the patient population as a whole. The observed associations between srp-27 overexpression and more aggressive tumors suggest a biologic role for srp-27 in human breast carcinomas.

Blotting, Western↗

PubMed1991

Changes in the stability of a human H3 histone mRNA during the HeLa cell cycle.

A major component of the regulation of histone protein synthesis during the cell cycle is the modulation of the half-life of histone mRNA. We have uncoupled transcriptional and posttranscriptional regulation by using a Drosophila hsp70-human H3 histone fusion gene that produces a marked human H3 histone mRNA upon heat induction. Transcription of this gene can be switched on and off by raising and lowering cell culture temperatures, respectively. HeLa cell lines containing stably integrated copies of the fusion gene were synchronized by double thymidine block. Distinct populations of H3 histone mRNA were produced by heat induction in early S-phase, late S-phase, or G2-phase cells, and the stability of the induced H3 histone mRNA was measured. The H3 histone mRNA induced during early S phase decayed with a half-life of 110 min, whereas the same transcript induced during late S phase had a half-life of 10 to 15 min. The H3 histone mRNA induced in non-S-phase cells is more stable than that induced in late S phase, with a half-life of 40 min. Thus, the stability of histone mRNA is actively regulated throughout the cell cycle. Our results are consistent with an autoregulatory model in which the stability of histone mRNA is determined by the level of free histone protein in the cytoplasm.

Cell Cycle↗

PubMed1989

Heat shock resistance conferred by expression of the human HSP27 gene in rodent cells.

Heat shock induces in cells the synthesis of specific proteins called heat shock proteins (HSPs) and a transient state of thermotolerance. The putative role of one of the HSPs, HSP27, as a protective molecule during thermal stress has been directly assessed by measuring the resistance to hyperthermia of Chinese hamster and mouse cells transfected with the human HSP27 gene contained in plasmid pHS2711. One- and two-dimensional gel electrophoresis of [3H]leucine- and [32P]orthophosphate-labeled proteins, coupled with immunological analysis using Ha27Ab and Hu27Ab, two rabbit antisera that specifically recognize the hamster and the human HSP27 protein respectively, were used to monitor expression and inducibility of the transfected and endogenous proteins. The human HSP27 gene cloned in pHS2711 is constitutively expressed in rodent cells, resulting in accumulation of the human HSP27 and all phosphorylated derivatives. No modification of the basal or heat-induced expression of endogenous HSPs is detected. The presence of additional HSP27 protein provides immediate protection against heat shock administered 48 h after transfection and confers a permanent thermoresistant phenotype to stable transfectant Chinese hamster and mouse cell lines. Mild heat treatment of the transfected cells results in an induction of the full complement of the endogenous heat shock proteins and a small increase in thermoresistance, but the level attained did not surpass that of heat-induced thermotolerant control cells. These results indicate that elevated levels of HSP27 is sufficient to give protection from thermal killing. It is concluded that HSP27 plays a major role in the increased thermal resistance acquired by cells after exposure to HSP inducers.

Animals↗

PubMed1989

Sequence and regulation of a gene encoding a human 89-kilodalton heat shock protein.

Vertebrate cells synthesize two forms of the 82- to 90-kilodalton heat shock protein that are encoded by distinct gene families. In HeLa cells, both proteins (hsp89 alpha and hsp89 beta) are abundant under normal growth conditions and are synthesized at increased rates in response to heat stress. Only the larger form, hsp89 alpha, is induced by the adenovirus E1A gene product (M. C. Simon, K. Kitchener, H. T. Kao, E. Hickey, L. Weber, R. Voellmy, N. Heintz, and J. R. Nevins, Mol. Cell. Biol. 7:2884-2890, 1987). We have isolated a human hsp89 alpha gene that shows complete sequence identity with heat- and E1A-inducible cDNA used as a hybridization probe. The 5'-flanking region contained overlapping and inverted consensus heat shock control elements that can confer heat-inducible expression on a beta-globin reporter gene. The gene contained 10 intervening sequences. The first intron was located adjacent to the translation start codon, an arrangement also found in the Drosophila hsp82 gene. The spliced mRNA sequence contained a single open reading frame encoding an 84,564-dalton polypeptide showing high homology with the hsp82 to hsp90 proteins of other organisms. The deduced hsp89 alpha protein sequence differed from the human hsp89 beta sequence reported elsewhere (N. F. Rebbe, J. Ware, R. M. Bertina, P. Modrich, and D. W. Stafford (Gene 53:235-245, 1987) in at least 99 out of the 732 amino acids. Transcription of the hsp89 alpha gene was induced by serum during normal cell growth, but expression did not appear to be restricted to a particular stage of the cell cycle. hsp89 alpha mRNA was considerably more stable than the mRNA encoding hsp70, which can account for the higher constitutive rate of hsp89 synthesis in unstressed cells.

Adenovirus Early Proteins↗

PubMed1988

Effect of heat shock on RNA metabolism in HeLa cells.

Incubation of HeLa cells at 42 degrees C results in pronounced inhibition of the accumulation of 18S and 28S ribosomal RNA (rRNA) and non-heat shock polyadenylated messenger RNA (mRNA) in the cytoplasm. Accumulation of transfer RNA and 5S ribosomal RNA is not affected. Transcription of rRNA precursor is reduced to approximately 50% of the 37 degrees C rate after 10 min of hyperthermia and declines to 30% of the control rate after 1 hr. In contrast, the accumulation of mature rRNA in the cytoplasm is inhibited more than 95%. Quantitative hybridization experiments and Northern blot analysis detect little accumulation of rRNA precursor sequences in nuclei, suggesting that the majority of the rRNA that is synthesized is degraded. Heat stress at 42 degrees C was found to have little effect on transcription of most non-heat shock mRNAs. However, accumulation of individual non-heat shock mRNAs in the cytoplasm proceeds at reduced rates. These results indicate that the primary effect of elevated temperature on RNA metabolism in mammalian cells is inhibition of processing and/or transport. Despite this, steady-state levels of abundant and rapidly turning over mRNA species remain unchanged during prolonged heat stress. We find that the half-life of c-myc mRNA increases greater than twofold at 42 degrees C. Thus, 42 degrees C heat stress appears to inhibit both accumulation and turnover of non-heat shock mRNA.

Cytoplasm↗