BORRELIA-BURGDORFERI SUPERCOILED PLASMIDS ENCODE MULTICOPY TANDEM OPEN READING FRAMES AND A LIPOPROTEIN GENE FAMILY

Citation
Sf. Porcella et al., BORRELIA-BURGDORFERI SUPERCOILED PLASMIDS ENCODE MULTICOPY TANDEM OPEN READING FRAMES AND A LIPOPROTEIN GENE FAMILY, Journal of bacteriology, 178(11), 1996, pp. 3293-3307
Citations number
54
Categorie Soggetti
Microbiology
Journal title
ISSN journal
00219193
Volume
178
Issue
11
Year of publication
1996
Pages
3293 - 3307
Database
ISI
SICI code
0021-9193(1996)178:11<3293:BSPEMT>2.0.ZU;2-7
Abstract
DNA sequencing and Southern blot analyses of a Borrelia burgdorferi DN A fragment encoding a signal sequence led to the discovery of a geneti c locus, designated 2.9, which appears to be present in at least seven copies in virulent B. burgdorferi 297. DNA sequence analysis of these regions revealed that each 2.9 locus contained an operon of four gene s (ABCD) and open reading frames designated rep(+) (positive strand) a nd rep(-) (negative strand) which encoded multiple repeat moths. Downs tream of the rep(+) gene(s) in six of the completely cloned and sequen ced 2.9 loci also were lipoprotein (LP) genes possessing highly simila r signal sequences but encoding variable mature polypeptides. The lipo proteins could be separated into two classes on the basis of hydrophil icity profiles, sequence similarities, and reactivity with specific an tibodies. The 2.9 loci were localized to two (20- and 30-kb) supercoil ed plasmids in B. burgdorferi 297. Northern (RNA) blot analysis establ ished that the 2.9 ABCD operon was only minimally expressed, whereas t he rep(-) gene(s) and at least three of the seven LP genes were expres sed by B. burgdorferi in vitro. A single putative promoter element was identified by RNA primer extension analysis upstream of the ABCD oper on, whereas a number of potential promoter regions existed upstream of the LP genes. The combined data indicate that the ABCD operon, rep(+) and rep(-) genes, and LP genes are separately transcribed during in v itro growth. The 2.9 loci possess a repetitiveness, diversity, and com plexity not previously described for B. burgdorferi; differential expr ession of these genes may facilitate the spirochete's ability to survi ve in diverse host environments.