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Aurora-A kinase is a one of the key regulators during mitosis progression. Aurora-A kinase is a potential target for anticancer therapies because overexpression of Aurora-A, which is frequently observed in some human cancers, results in aberrant mitosis leading to chromosomal instability and possibly tumorigenesis. MK-5108 is a novel small molecule with potent inhibitory activity against Aurora-A kinase. Although most of the Aurora-kinase inhibitors target both Aurora-A and Aurora-B, MK-5108 specifically inhibited Aurora-A kinase in a panel of protein kinase assays. Inhibition of Aurora-A by MK-5108 in cultured cells induced cell cycle arrest at the G2-M phase in flow cytometry analysis. The effect was confirmed by the accumulation of cells with expression of phosphorylated Histone H3 and inhibition of Aurora-A autophosphorylation by immunostaining assays. MK-5108 also induced phosphorylated Histone H3 in skin and xenograft tumor tissues in a nude rat xenograft model. MK-5108 inhibited growth of human tumor cell lines in culture and in different xenograft models. Furthermore, the combination of MK-5108 and docetaxel showed enhanced antitumor activities compared with control and docetaxel alone–treated animals without exacerbating the adverse effects of docetaxel. MK-5108 is currently tested in clinical trials and offers a new therapeutic approach to combat human cancers as a single agent or in combination with existing taxane therapies. Mol Cancer Ther; 9(1); 157–66

The correlation between mutations in the Werner's syndrome (WRN) gene and the haplotypes of surrounding markers was studied in Japanese patients. We have elucidated the genomic structure of WRN helicase, and found five additional mutations, designated mutations 6-10. Mutations 4 and 6 were found to be the two major mutations in this population; these mutations comprised 50.8% and 17.5%, respectively, of the total in a sample of 126 apparently unrelated chromosomes. Almost all the patients homozygous for mutation 4 shared a haplotype around the WRN gene, consistent with the view that they are derived from a single ancestor. This important advantage demonstrated in the identification of the WRN gene suggests that the Japanese present a unique population for the cloning of other disease genes. The conserved haplotype was observed across 19 loci, extending a distance estimated to be more than 1.4 Mbp around the WRN gene. This haplotype is rare among random Japanese individuals. Unexpectedly, all the nine patients homozygous for mutation 6 shared a haplotype that was identical to this haplotype at 18 of these 19 markers. These results suggest that mutations 4 and 6 arose independently in almost identical rare haplotypes. The remaining mutations (1, 5, 7, 8, 9, and 10) occurred rarely, and were each associated with different haplotypes.

Separase is an evolutionarily conserved protease that is essential for chromosome segregation and cleaves cohesin Scc1/Rad21, which joins the sister chromatids together. Although mammalian separase also functions in chromosome segregation, our understanding of this process in mammals is still incomplete. We generated separase knockout mice, reporting an essential function for mammalian separase. Separase-deficient mouse embryonic fibroblasts exhibited severely restrained increases in cell number, polyploid chromosomes, and amplified centrosomes. Chromosome spreads demonstrated that multiple chromosomes connected to a centromeric region. Live observation demonstrated that the chromosomes of separase-deficient cells condensed, but failed to segregate, although subsequent cytokinesis and chromosome decondensation proceeded normally. These results establish that mammalian separase is essential for the separation of centromeres, but not of the arm regions of chromosomes. Other cell cycle events, such as mitotic exit, DNA replication, and centrosome duplication appear to occur normally. We also demonstrated that heterozygous separase-deficient cells exhibited severely restrained increases in cell number with apparently normal mitosis in the absence of securin, which is an inhibitory partner of separase.

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The list of human RecQ helicase comprises RecQ1, BLM (Bloom syndrome), WRN (Werner syndrome), RTS (Rothmund-Thomson syndrome), and RecQ5. Of these, the defective BLM, WRN, and RTS helicases are responsible for distinct but overlapping clinical features suggesting premature aging and an enhanced risk of cancer, which apparently stems from chromosomal instability in the cells of tissues and organs where expression of the helicase genes are specified. In an effort to obtain an animal model for these diseases, we performed gene target experiments to generate the WRN and RTS knockout mice.

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A unique gene, RBP-MS, spanning over 230 kb in the human chromosome 8pll-12 near the Werner syndrome gene locus is described. The single-copy RBP-MS gene is alternatively spliced, resulting in a family of at least 12 transcripts (average length of 1.5 kb). Nine different types of cDNAs that encode an RNA-binding motif at the N terminus and helix-rich sequences at the C terminus have been identified thus far. Among the 16 exons identified, four 5'-proximal exons contained sequences homologous to the RNAbinding domain of Drosophila couch potato gene. Northern blot analysis showed that the RBP-MS gene was expressed strongly in the heart, prostate, intestine, and ovary, and poorly in the skeletal muscle, spleen, thymus, brain, and peripheral leukocytes. The possible role of this gene in RNA metabolism is discussed.Several genes of medical importance map to the short arm of chromosome 8, including the tumor suppressor genes implicated in the pathogenesis of colorectal carcinoma and prostate cancer (1, 2) and the gene responsible for Werner syndrome (WS), a rare autosomal recessive disorder characterized by the premature aging (3-7). Recently, Yu and coworkers cloned a DNA helicase gene as a candidate for WS gene from the 8pl 1-12 region (8). As part of similar efforts to identify the WS gene as well as other disease-related genes, we established a 1.3-megabase physical map spanning the WS region and localized known and novel genes in this interval. These efforts facilitated the physical mapping of the sequence-tagged site and known genes such as those encoding for glutathione S-reductase (GSR), transcription factor IIE ,3 subunit (TFIIEf3), and protein phosphatase 2A f3 subunit (PP2A 4) on chromosome 8pll-12. In addition, analysis by a dual-color fluorescence in situ hybridization analysis enabled us to estimate the precise distances between the genomic markers and genes (9).The WS region was cloned in P1. Exon trapping was used to identify novel gene(s) occurring in this important region. Candidate exons were used in searches of the public data bases and also used to screen cDNA libraries. One novel gene obtained through the processes was of particular interest, as this gene is in close proximity to the closest genetic markers to the WS gene, D8S339 and D8S1055 (10,11). Further interest in this gene was strengthened by its unique features and complex genomic structure.Sequence analysis of cloned cDNAs and genomic DNA showed that this gene, referred to as RBP-MS (RNA-binding protein gene with multiple splicing), produces multiple transcripts by differential splicing and codes for a family of RNA-binding proteins. The RNA-binding motif region shared in all the predicted proteins is highly homologous to that of Drosophila couch potato proteins implicated in the regulation of peripheral nervous system development in the embryo (12). Initial studies in gene cloning and Northern analysis revealed that the transcripts were rather short (1.5 kb) despite the finding that the gene was as long as 230 kb.This paper desc...