Identification of a novel gene--SSK1--in human endothelial cells exposed to shear stress

Gene profiling techniques and their application in angiogenesis and vascular development

The analysis of gene expression in specific tissues and physiological processes has evolved over the last 20 years from the painstaking identification of selected genes to the relatively efficient and open-ended surveying of potentially all genes expressed in a tissue. Current art for gene discovery includes the use of large-scale arrays of cDNA sequences or oligonucleotides, and molecular 'tagging' techniques such as GeneCalling and SAGE. Common to each of these techniques is a reliance on the increasingly comprehensive databases of human and mouse EST and full-length gene sequences. Early efforts to characterize candidate genes were limited by their narrow scope, while current efforts are confounded by the enormous volume of data returned. Sophisticated software tools are an integral part of the analysis, helping to organize information into coherent groups with temporal or functional similarity. These techniques, in conjunction with the continued analysis of human genetic syndromes, transgenic, and knockout mice, have driven genetic analysis of angiogenesis and vascular development from describing which individual genes are involved to defining the outlines of regulatory networks.

p55CDC/hCDC20 is associated with BUBR1 and may be a downstream target of the spindle checkpoint kinase

Eukaryotic cells have evolved a mechanism that delays the progression of mitosis until condensed chromosomes are properly positioned on the mitotic spindle. We have been studying genes that regulated the spindle checkpoint in human cells. Enforced expression of human BUBR1, but not a BUBR1 mutant allele, enhances accumulation of mitotic cells. Yeast two-hybrid system and GST-pulldown analyses show that p55CDC/hCdc20, a protein known to link spindle checkpoint components such as MAD2 to anaphase promoting complex (APC), interacts with BUBR1. In addition, p55CDC is capable of pulling down BUBR1 in sf-9 cells infected with both p55CDC and His6-BUBR1 recombinant baculoviruses but not in the cells infected with p55CDC baculoviruses or with the baculoviral vector alone. Moreover, immunoprecipitation followed by Western blot analyses confirmed that native p55CDC is associated with BUBR1 in HeLa cells. Spindle checkpoint activation by nocodazole treatment enhances the association between p55CDC and His6-BUBR1. In nocodazole-arrested mitotic cells, both CDC16 and hyperphosphorylated CDC27, two APC components, preferentially associate with His6-BUBR1 resins, but not the control resins. Furthermore, BUBR1 phosphorylates p55CDC in vitro, and the phosphorylation of p55CDC by BUBR1 appears to be correlated with spindle checkpoint activation. Together, our studies strongly suggest that BUBR1 may target APC via p55CDC.

Identification of genes responsive to BPDE treatment in HeLa cells using cDNA expression assays

Genotoxic stresses induce cellular responses that can be observed at the level of gene expression. We have studied changes in gene expression following BPDE exposure in HeLa cells by using a cDNA expression array of 597 human genes. After a 53-hr exposure to 0.4 microM BPDE, nine genes were upregulated. The protein products of these genes are: fos-related antigen 2, apoptotic cysteine protease MCH4, DB1 (zinc finger protein 91), transcription factor ETR103, integrin alpha, interleukin-4, interleukin-6, 23-kDa highly basic protein, and ribosomal protein S9. We observed the downregulation of gene expression of three genes: heat-shock protein 27, DNA-binding protein TAX, and NADH-ubiquinone oxidoreductase B18 subunit. These results suggest unknown functions or regulatory circuits for several of the responsive genes and demonstrate the complexity of cellular responses to genotoxic insults.

Differentially expressed genes in activin-induced apoptotic LNCaP cells

Gene transcripts differentially expressed in activin-induced human prostatic LNCaP apoptotic cells have been discovered by an improved subtractive hybridization method, uracil-DNA subtraction assay (USA), which involves digestion with uracil-DNA glycosylase and mung-bean nuclease. Among the five up-regulated and seven down-regulated genes, we have identified six known (>95% homology and similar size; p16, p53, Siva, RHAMM, Pax2, and eIF-4a1), three homologues (>95% homology but different size; myosin, a helicase motif, and a kinase motif), and three novel genes (no homology). In addition, anti-sense knock-out of a resulting novel kinase-like gene was found to abolish the apoptotic DNA fragmentation in activin-treated LNCaP cells. These findings indicate a new potential mechanism in DNA fragmentation of activin-induced cell-cycle arresting and apoptosis.