Biomedical subjects

Nicola Wiechens

Publications and source records attributed to Nicola Wiechens.

5 recordsLinked to original sources

PubMed2006

Nucleosome dynamics.

In the 30 years since the discovery of the nucleosome, our picture of it has come into sharp focus. The recent high-resolution structures have provided a wealth of insight into the function of the nucleosome, but they are inherently static. Our current knowledge of how nucleosomes can be reconfigured dynamically is at a much earlier stage. Here, recent advances in the understanding of chromatin structure and dynamics are highlighted. The ways in which different modes of nucleosome reconfiguration are likely to influence each other are discussed, and some of the factors likely to regulate the dynamic properties of nucleosomes are considered.

Adenosine Triphosphate↗

PubMed2004

The FHA domain protein SNIP1 is a regulator of the cell cycle and cyclin D1 expression.

Smad nuclear interacting protein 1 (SNIP1) is an evolutionarily conserved protein containing a forkhead-associated (FHA) domain that regulates gene expression through interactions with multiple transcriptional regulators. Here, we have used short interfering RNAs (siRNAs) to knockdown SNIP1 expression in human cell lines. Surprisingly, we found that reduction in SNIP1 levels resulted in significantly reduced cell proliferation and accumulation of cells in the G1 phase of the cell cycle. Consistent with this result, we observed that cyclin D1 protein and mRNA levels were reduced. Moreover, SNIP1 depletion results in inhibition of cyclin D1 promoter activity in a manner dependent upon a previously characterized binding site for the AP-1 transcription factor family. SNIP1 itself is induced upon serum stimulation immediately prior to cyclin D1 expression. These effects were independent of the tumour suppressors p53 and retinoblastoma (Rb), but were consistent with an interaction with BRG1, a component of the ATP-dependent chromatin remodelling complex, Swi/Snf. These results define both a new function for SNIP1 and identify a previously unrecognized regulator of the cell cycle and cyclin D1 expression.

Base Sequence↗

PubMed2004

Sin mutations alter inherent nucleosome mobility.

Previous studies have identified sin mutations that alleviate the requirement for the yeast SWI/SNF chromatin remodelling complex, which include point changes in the yeast genes encoding core histones. Here we characterise the biochemical properties of nucleosomes bearing these mutations. We find that sin mutant nucleosomes have a high inherent thermal mobility. As the SWI/SNF complex can alter nucleosome positioning, the higher mobility of sin mutant nucleosomes provides a means by which sin mutations may substitute for SWI/SNF function. The location of sin mutations also provides a new opportunity for insights into the mechanism for nucleosome mobilisation. We find that both mutations altering histone DNA contacts at the nucleosome dyad and mutations in the dimer-tetramer interface influence nucleosome mobility. Furthermore, incorporation of H2A.Z into nucleosomes, which also alters dimer-tetramer interactions, affects nucleosome mobility. Thus, variation of histone sequence or subtype provides a means by which eukaryotes may regulate access to chromatin through alterations to nucleosome mobility.

Calcium Chloride↗

PubMed2003

Nucleo-cytoplasmic shuttling of Axin, a negative regulator of the Wnt-beta-catenin Pathway.

Axin is a negative regulator of the Wnt pathway essential for down-regulation of beta-catenin. Axin has been considered so far as a cytoplasmic protein. Here we show that, although cytoplasmic at steady state, Axin shuttles in fact in and out of the nucleus; Axin accumulates in the nucleus of cells treated with leptomycin B, a specific inhibitor of the CRM1-mediated nuclear export pathway and is efficiently exported from Xenopus oocyte nuclei in a RanGTP- and CRM1-dependent manner. We have characterized the sequence requirement for export and identified two export domains, which do not contain classical nuclear export consensus sequences, and we show that Axin binds directly to the export factor CRM1 in the presence of RanGTP.

Active Transport, Cell Nucleus↗

PubMed2002

Sialylation is essential for early development in mice.

Sialic acids are widely expressed as terminal carbohydrates on glycoconjugates of eukaryotic cells. Sialylation is crucial for a variety of cellular functions, such as cell adhesion or signal recognition, and regulates the biological stability of glycoproteins. The key enzyme of sialic acid biosynthesis is the bifunctional UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (UDP-GlcNAc 2-epimerase), which catalyzes the first two steps of sialic acid biosynthesis in the cytosol. We report that inactivation of the UDP-GlcNAc 2-epimerase by gene targeting causes early embryonic lethality in mice, thereby emphasizing the fundamental role of this bifunctional enzyme and sialylation during development. The need of UDP-GlcNAc 2-epimerase for a defined sialylation process is exemplified with the polysialylation of the neural cell adhesion molecule in embryonic stem cells.

Alleles↗