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The publication of the draft sequence of the mouse genome creates a powerful new resource for the biomedical community. Access to the sequence will undoubtedly improve the ways in which the various reagents and tools of mouse biology are used for understanding the molecular basis for human physiology, development and disease.
For DNA replication to proceed through heterochromatin, the replication machinery must negotiate the highly condensed chromatin. A new study shows that an ACF1–ISWI chromatin remodeling complex is required for the replication of pericentromeric heterochromatin. This complex may act to unravel chromatin structure in these regions of the genome, thereby permiting movement of the replication fork.
Enhancer elements act from distal regions to mediate the transcription of genes. A novel combination of FISH and ChIP techniques may provide new insight into the mechanism by which enhancer elements exert their control. Application of the technique to the Hbb (encoding β-globin) locus control region (LCR) suggests that elements of the LCR may be in close proximity to the transcribed β-globin genes.
Pluripotent stem cells are essential for embryonic development and regeneration of adult tissues. But when the molecular pathways that control stem cells go awry, the result can often be the development of tumors. Wnt signaling mediated by the intracellular transducer β-catenin and the tumor suppressor APC (adenomatosis polyposis coli) is pivotal in embryogenesis and frequently associated with cancer. The investigation of different mutations in Apc that lead to increased levels of β-catenin in pluripotent cells supports the notion that many cancers may result from the dysregulation of stem-cell programs.
A new study identifies a cell-autonomous two-hour clock in diverse types of mammalian cells in culture. The two-hour oscillations depend on negative feedback of a gene product, Hes1, on transcription of its own gene—a regulatory mechanism that is identical to the circadian clock. Although a similar two-hour clock is required for vertebrate somitogenesis, the physiological role of the two-hour clock in cells remains unclear.