Chromosome

About: Chromosome is a research topic. Over the lifetime, 17538 publications have been published within this topic receiving 660077 citations. The topic is also known as: chromosomes & GO:0005694.

Small-cell lung cancer is characterized by a high incidence of deletions on chromosomes 3p, 4q, 5q, 10q, 13q and 17p

Abstract: The genetic mechanisms that define the malignant behaviour of small-cell lung cancer (SCLC) are poorly understood. We performed comparative genomic hybridization (CGH) on 22 autoptic SCLCs to screen the tumour genome for genomic imbalances. DNA loss of chromosome 3p was a basic alteration that occurred in all tumours. Additionally, deletions were observed on chromosome 10q in 94% of tumours and on chromosomes 4q, 5q, 13q and 17p in 86% of tumours. DNA loss was confirmed by loss of heterozygosity (LOH) analysis for chromosomes 3p, 5q and 10q. Simultaneous mutations of these six most abundant genetic changes were found in 12 cases. One single tumour carried at least five deletions. DNA under-representations were observed less frequently on chromosome 15q (55%) and chromosome 16q (45%). The prevalent imbalances were clearly indicated by the superposition of the 22 tumours to a CGH superkaryogram. In our view, the high incidence of chromosomal loss is an indication that SCLC is defined by a pattern of deletions and that the inactivation of multiple growth-inhibitory pathways contributes in particular to the aggressive phenotype of that type of tumour.

Soil To Genomics: The Streptomyces Chromosome

Abstract: The 8-9-Mb Streptomyces chromosome is linear, with a "core" containing essential genes and "arms" carrying conditionally adaptive genes that can sustain large deletions in the laboratory. Bidirectional chromosome replication from a central oriC is completed by "end-patching," primed from terminal proteins covalently bound to the free 5'-ends. Plasmid-mediated conjugation involves movement of double-stranded DNA by proteins resembling other bacterial motor proteins, probably via hyphal tip fusion, mediated by these transfer proteins. Circular plasmids probably transfer chromosomes by transient integration, but linear plasmids may lead the donor chromosome end-first into the recipient by noncovalent association of ends. Transfer of complete chromosomes may be the rule. The recipient mycelium is colonized by intramycelial spreading of plasmid copies, under the control of plasmid-borne "spread" genes. Chromosome partition into prespore compartments of the aerial mycelium is controlled in part by actin- and tubulin-like proteins, resembling MreB and FtsZ of other bacteria.

Senescence of Nickel-Transformed Cells by an X Chromosome: Possible Epigenetic Control

Abstract: Transfer of a normal Chinese hamster X chromosome (carried in a mouse A9 donor cell line) to a nickel-transformed Chinese hamster cell line with an Xq chromosome deletion resulted in senescense of these previously immortal cells. At early passages of the A9/CX donor cells, the hamster X chromosome was highly active, inducing senescence in 100% of the colonies obtained after its transfer into the nickel-transformed cells. However, senescence was reduced to 50% when Chinese hamster X chromosomes were transferred from later passage A9 cells. Full senescing activity of the intact hamster X chromosome was restored by treatment of the donor mouse cells with 5-azacytidine, which induced demethylation of DNA. These results suggest that a senescence gene or genes, which may be located on the Chinese hamster X chromosome, can be regulated by DNA methylation, and that escape from senescence and possibly loss of tumor suppressor gene activity can occur by epigenetic mechanisms.

KOPS: DNA motifs that control E. coli chromosome segregation by orienting the FtsK translocase

Abstract: Bacterial chromosomes are organized in replichores of opposite sequence polarity. This conserved feature suggests a role in chromosome dynamics. Indeed, sequence polarity controls resolution of chromosome dimers in Escherichia coli. Chromosome dimers form by homologous recombination between sister chromosomes. They are resolved by the combined action of two tyrosine recombinases, XerC and XerD, acting at a specific chromosomal site, dif, and a DNA translocase, FtsK, which is anchored at the division septum and sorts chromosomal DNA to daughter cells. Evidences suggest that DNA motifs oriented from the replication origin towards dif provide FtsK with the necessary information to faithfully distribute chromosomal DNA to either side of the septum, thereby bringing the dif sites together at the end of this process. However, the nature of the DNA motifs acting as FtsK orienting polar sequences (KOPS) was unknown. Using genetics, bioinformatics and biochemistry, we have identified a family of DNA motifs in the E. coli chromosome with KOPS activity.