Genetic selection has been used to isolate second-site suppressors of a
defective cold-sensitive initiation factor I (IF1) R69L mutant ofEscherichia
coli. The suppressor mutants specifically map to a single rRNA operon on a
plasmid in a strain with all chromosomal rRNA operons deleted.
HMGN1 is a nuclear protein that binds to nucleosomes and alters the
accessibility of regulatory factors to their chromatin targets. To elucidate
its biological function and identify specific HMGN1 target genes, we gener-ated Hmgn1–⁄– mice. DNA microarray analysis of Hmgn1+⁄+ and
Hmgn1–⁄– embryonic fibroblasts identified N-cadherin as a potential
HMGN1 gene target.
It is a great pleasure to introduce volume 19 of
the book series Monographs in Human Genetics
entitled ‘Craniosynostoses: Molecular Genetics,
Principles of Diagnosis and Treatment’. The initial
idea for this book was born during a workshop
on craniosynostoses held at the Academy
of Human Genetics in Würzburg (Germany).
Hartmut Collmann and Wolfram Kress brought
together many seemingly diverse aspects of craniosynostoses,
including clinical approaches, genetics,
molecular mechanisms and, most importantly,
Chromosomal Instability in Solid Tumors Solid tumors are generally highly aneuploid, containing an abnormal number of chromosomes; these chromosomes also exhibit structural alterations such as translocations, deletions, and amplifications. Again, colon cancer has proven to be a particularly useful model for the study of chromosomal instability (CIN). As described above, some familial cases are characterized by the presence of MIN.
Gonococcal Resistance to Antimicrobial Agents
It is no surprise that N. gonorrhoeae, with its remarkable capacity to alter its antigenic structure and adapt to changes in the microenvironment, has become resistant to numerous antibiotics. The first effective agents against gonorrhea were the sulfonamides, which were introduced in the 1930s and became ineffective within a decade. Penicillin was then employed as the drug of choice for the treatment of gonorrhea. By 1965, 42% of gonococcal isolates had developed lowlevel resistance to penicillin G.
Clinically important resistance to vancomycin was first described among enterococci in France in 1988. Vancomycin-resistant enterococci (VRE) have subsequently become disseminated worldwide. The genes encoding resistance are carried on plasmids that can transfer themselves from cell to cell and on transposons that can jump from plasmids to chromosomes. Resistance is mediated by enzymes that substitute D-lactate for D-alanine on the peptidoglycan stem peptide so that there is no longer an appropriate target for vancomycin binding.
Alterations in chromatin packing are not the only
physical manifestations of cancer. A cluster of tumour
cells will also usually display gross structural changes
that pathologists use for diagnosis: cells look visibly
deformed and are often enlarged, with swollen and
misshapen nuclei; and the chromosomes are distri-
buted eccentrically. In an attempt to study these chan-
ges more accurately, researchers at ASU’s Biodesign
Institute have developed an optical computerized
tomography (CT) scan for individual cells.