Chromosomal Q-heterochromatin regions in the indigenous population of the northern part of West Siberia and in new migrants

The variability of Q-heterochromatin regions (Q-HR) was studied in native residents of the northern part of West Siberia, viz Yakuts (n = 127), Selkups (n = 90) and Khants (n = 54), as well as in newcomers including oil-borers (n = 43) and children (n = 113) living permanently in this part of the USSR. The major quantitative characteristics of chromosomal Q-HR variability were shown to be very similar in oil-borers and natives, and this is considered to be the result of specific selection of individuals according to the amount of Q-HRs in their genome. The hypothesis on the possible selective value of chromosomal Q-HRs in human adaptation to extreme environmental conditions of the extreme north is discussed.     

Oleoyl Coenzyme A Regulates Interaction of Transcriptional Regulator RaaS (Rv1219c) with DNA in Mycobacteria

We have recently shown that RaaS (regulator of antimicrobial-assisted survival), encoded by Rv1219c in Mycobacterium tuberculosis and by bcg_1279c in Mycobacterium bovis bacillus Calmette-Guérin, plays an important role in mycobacterial survival in prolonged stationary phase and during murine infection. Here, we demonstrate that long chain acyl-CoA derivatives (oleoyl-CoA and, to lesser extent, palmitoyl-CoA) modulate RaaS binding to DNA and expression of the downstream genes that encode ATP-dependent efflux pumps. Moreover, exogenously added oleic acid influences RaaS-mediated mycobacterial improvement of survival and expression of the RaaS regulon. Our data suggest that long chain acyl-CoA derivatives serve as biological indicators of the bacterial metabolic state. Dysregulation of efflux pumps can be used to eliminate non-growing mycobacteria.     

A family of autocrine growth factors in Mycobacterium tuberculosis

Mycobacterium tuberculosis and its close relative, Mycobacterium bovis (BCG) contain five genes whose predicted products resemble Rpf from Micrococcus luteus. Rpf is a secreted growth factor, active at picomolar concentrations, which is required for the growth of vegetative cells in minimal media at very low inoculum densities, as well as the resuscitation of dormant cells. We show here that the five cognate proteins from M. tuberculosis have very similar characteristics and properties to those of Rpf. They too stimulate bacterial growth at picomolar (and in some cases, subpicomolar) concentrations. Several lines of evidence indicate that they exert their activity from an extra-cytoplasmic location, suggesting that they are also involved in intercellular signalling. The five M. tuberculosis proteins show cross-species activity against M. luteus, Mycobacterium smegmatis and M. bovis (BCG). Actively growing cells of M. bovis (BCG) do not respond to these proteins, whereas bacteria exposed to a prolonged stationary phase do. Affinity-purified antibodies inhibit bacterial growth in vitro, suggesting that sequestration of these proteins at the cell surface might provide a means to limit or even prevent bacterial multiplication in vivo. The Rpf family of bacterial growth factors may therefore provide novel opportunities for preventing and controlling mycobacterial infections.     

pH-dependent changes in structure and RNA-binding activity of casein kinase 2 from Rana temporaria oocytes

It is demonstrated by filter-binding assay that casein kinase 2 from Rana temporaria oocytes binds rRNA in vitro with high affinity. Ligand-blotting shows that rRNA-binding activity is inherent to alpha and alpha' subunits of the enzyme. Increase of pH from 6.5 to 7.5 has little effect on casein kinase but completely suppresses rRNA-binding activity of the enzyme. Sedimentation coefficient of casein kinase 2 also depends on pH: at pH 7.5 it is mainly 10 S, and at pH 6.5-18 S. At pH 6.95 the amounts of both forms are equal. The heavy form of casein kinase 2 practically lacks rRNA-binding activity.     

The rpf gene of Micrococcus luteus encodes an essential secreted growth factor

Micrococcus luteus secretes a small protein called Rpf, which has autocrine and paracrine signalling functions and is required for the resuscitation of dormant cells. Originally isolated from the supernatant of actively growing cultures, Rpf was also detected on the surface of actively growing bacteria. Most molecules may be sequestered non-productively at the cell surface, as a truncated form of the protein, encompassing only the 'Rpf domain' is fully active. The C-terminal LysM module, which probably mediates binding to the cell envelope, is not required for biological activity. Rpf was essential for growth of M. luteus. Washed cells, inoculated at low density into a minimal medium, could not grow in its absence. Moreover, the incorporation of anti-Rpf antibodies into the culture medium at the time of inoculation also prevented bacterial growth. We were unable to inactivate rpf using a disrupted form of the gene, in which most of the coding sequence was replaced with a selectable thiostrepton resistance marker. Gene disruption was possible in the presence of a second, functional, plasmid-located copy of rpf, but not in the presence of a rpf derivative whose protein product lacked the secretory signal sequence. As far as we are aware, Rpf is the first example of a truly secreted protein that is essential for bacterial growth. If the Rpf-like proteins elaborated by Mycobacterium tuberculosis and other mycobacteria prove similarly essential, interference with their proper functioning may offer novel opportunities for protecting against, and treating, tuberculosis and other mycobacterial disease.     

The external PASTA domain of the essential serine/threonine protein kinase PknB regulates mycobacterial growth

PknB is an essential serine/threonine protein kinase required for mycobacterial cell division and cell-wall biosynthesis. Here we demonstrate that overexpression of the external PknB_PASTA domain in mycobacteria results in delayed regrowth, accumulation of elongated bacteria and increased sensitivity to β-lactam antibiotics. These changes are accompanied by altered production of certain enzymes involved in cell-wall biosynthesis as revealed by proteomics studies. The growth inhibition caused by overexpression of the PknB_PASTA domain is completely abolished by enhanced concentration of magnesium ions, but not muropeptides. Finally, we show that the addition of recombinant PASTA domain could prevent regrowth of Mycobacterium tuberculosis, and therefore offers an alternative opportunity to control replication of this pathogen. These results suggest that the PknB_PASTA domain is involved in regulation of peptidoglycan biosynthesis and maintenance of cell-wall architecture.