Mitotic checkpoints, genetic instability, and cancer

A Small-Molecule AIE Chromosome Periphery Probe for Cytogenetic Studies

The chromosome periphery (CP) is a complex network that covers the outer surface of chromosomes. It acts as a carrier of nucleolar components, helps maintain chromosome structure, and plays an important role in mitosis. Current methods for fluorescence imaging of CP largely rely on immunostaining. We herein report a small-molecule fluorescent probe, ID-IQ, which possesses aggregation-induced emission (AIE) property, for CP imaging. By labelling the CP, ID-IQ sharply highlighted the chromosome boundaries, which enabled rapid segmentation of touching and overlapping chromosomes, direct identification of the centromere, and clear visualization of chromosome morphology. ID-IQ staining was also compatible with fluorescence in situ hybridization and could assist the precise location of the gene in designated chromosome. Altogether, this study provides a versatile cytogenetic tool for improved chromosome analysis, which greatly benefits the clinical diagnostic testing and genomic research.

Ki-67 and the Chromosome Periphery Compartment in Mitosis

The chromosome periphery is a complex network of proteins and RNA molecules (many derived from nucleoli) that covers the outer surface of chromosomes and whose function remains mysterious. Although it was first described over 130 years ago, technological advances and the recent discovery that Ki-67 acts as an organiser of this region have allowed the chromosome periphery to be dissected in previously unattainable detail, leading to a revival of interest in this obscure chromosomal compartment. Here, we review the most recent advances into the composition, structure and function of the chromosome periphery, discuss possible roles of Ki-67 during mitosis and consider why this structure is likely to remain the focus of ongoing attention in the future.

Stationary phase mutagenesis in B. subtilis: a paradigm to study genetic diversity programs in cells under stress

One of the experimental platforms to study programs increasing genetic diversity in cells under stressful or nondividing conditions is adaptive mutagenesis, also called stationary phase mutagenesis or stress-induced mutagenesis. In some model systems, there is evidence that mutagenesis occurs in genes that are actively transcribed. Some of those genes may be actively transcribed as a result of environmental stress giving the appearance of directed mutation. That is, cells under conditions of starvation or other stresses accumulate mutations in transcribed genes, including those transcribed because of the selective pressure. An important question concerns how, within the context of stochastic processes, a cell biases mutation to genes under selection pressure? Because the mechanisms underlying DNA transactions in prokaryotic cells are well conserved among the three domains of life, these studies are likely to apply to the examination of genetic programs in eukaryotes. In eukaryotes, increasing genetic diversity in differentiated cells has been implicated in neoplasia and cell aging. Historically, Escherichia coli has been the paradigm used to discern the cellular processes driving the generation of adaptive mutations; however, examining adaptive mutation in Bacillus subtilis has contributed new insights. One noteworthy contribution is that the B. subtilis' ability to accumulate chromosomal mutations under conditions of starvation is influenced by cell differentiation and transcriptional derepression, as well as by proteins homologous to transcription and repair factors. Here we revise and discuss concepts pertaining to genetic programs that increase diversity in B. subtilis cells under nutritional stress.