Fission yeast cdc21, a member of the MCM protein family, is required for onset of S phase and is located in the nucleus throughout the cell cycle.

The fission yeast cdc21 protein belongs to the MCM family, implicated in the once per cell cycle regulation of chromosome replication. In budding yeast, proteins in this family are eliminated from the nucleus during S phase, which has led to the suggestion that they may serve to distinguish unreplicated from replicated DNA, as in the licensing factor model. We show here that, in contrast to the situation in budding yeast, cdc21 remains in the nucleus after S phase, as is found for related proteins in mammalian cells.

Purification of a HeLa cell nuclear protein that binds selectively to DNA irradiated with ultra-violet light.

Ultraviolet (UV) light induces a variety of lesions in DNA of which the pyrimidine dimer represents the major species. Pyrimidine dimers exist as both a cyclobutane type and a 6-4' (pyrimidine-2'-one) photoproduct. We have purified a protein of M(r) approximately 125,000 from HeLa cell nuclei which binds efficiently to double-stranded DNA irradiated with UV light but not to undamaged DNA.

Position-independent, high-level expression of the human beta-globin gene in transgenic mice.

We have constructed a "minilocus" that contains the 5' and 3' flanking regions of the human beta-globin locus and the beta-globin gene. These regions are characterized by erythroid-specific DNAase I-superhypersensitive sites and are normally located approximately 50 kb 5' and 20 kb 3' of the beta-globin gene. This minilocus is expressed tissue-specifically in transgenic mice at a level directly related to its copy number yet independent of its position of integration in the genome.

The regulation of expression of human beta-globin genes.

We have analyzed the regulation of expression of the human beta-globin gene by DNA mediated gene transfer in MEL cells and microinjection in fertilized mouse eggs. The results show that the beta-globin gene contains two regulatory elements: one element in the promoter, that is required for full transcriptional activity and, secondly, a tissue and developmental specific enhancer 3' to the gene.