Structure Of Hotspots Research Articles

Structure and function of hot spots providing signals for site‐directed specific recombination and gene expression in Tn21 transposons

Tn21- and Tn3-related transposons are widespread and carry various resistance determinants. The insertion points of different resistance genes were precisely defined in Tn2424, Tn1696, Tn2410, Tn4000 and its derivatives and compared to the corresponding sites in Tn7, pSA, R388, R46, Tn2603, Tn1331 and in Tn3-related elements. Insertional 'hot spots' located at the 3' end of different genes comprised 55 nucleotides and yielded more than 90% homology to the corresponding consensus sequence, termed hs1. Elements of this class were found to direct recA-independent generation of deletions. Flanking the 5' ends, hs2 (CTAAAACAAAGTTA) comprised the terminal nucleotides of hs1. Functional properties of hot spots as recognition sites for site-specific recombination and regulation of gene expression indicate that they might be involved in transfer, stable inheritance and expression of prokaryotic genes.

Infrared array imaging and spectrophotometry of the nuclear region of the 'hot-spot' galaxy NGC 2903

Previous studies of the hot-spot galaxy NGC 2903 at a variety of wavelengths have shown that considerable star formation is occurring within the complex hot-spot structures in this galaxy's nuclear region. A K-band (2.2 microns) image of the galaxy's nuclear region has been obtained with an infrared CCD and compared to V-band (0.55 micron) and 1-micron images of the same region. The data show that changes in hot spot morphology in the V band are due primarily to variations in extinction, though variations in stellar populations and densities are also probably important. The K-band/V-band image ratio has been used to map the variation of color across the inner about 20 arcsec of the galaxy. The structures revealed in this image ratio suggest that a dust lane extends through the nucleus. Spectrophotometry of the Br-alpha hydrogen recombination line emission from two positions within the imaged region has also been acquired. The measured line strengths show that ionized gas and active star formation exist well outside of the hot spots. 36 references.

Structure of chi hotspots of generalized recombination

Chi recombinational hotspots are sites around which the rate of Rec-promoted recombination in bacteriophage λ is elevated. Examination of a derivative of λ into which the plasmid pBR322 was inserted reveals that pBR322 lacks Chi sites. Using this λ-pBR322 hybrid, we obtained mutations creating Chi sites at three widely separated loci within pBR322. Nucleotide sequence analysis reveals that the mutations are single base-pair changes creating the octamer 5′ GCTGGTGG 3′. This sequence is present at three previously analyzed Chi sites in λ, and all analyzed mutations creating or inactivating these Chi sites occur within this octamer. We conclude that Chi is 5′ GCTGGTGG 3′, or its complement, or both.