TY - JOUR
T1 - Effects of growth conditions on expression of mycobacterial murA and tyrS genes and contributions of their transcripts to precursor rRNA synthesis
AU - Gonzalez V Merchand, J. A.
AU - Colston, M. J.
AU - Cox, R.
PY - 1999
Y1 - 1999
N2 - All mycobacteria studied to date have an rRNA operon, designated rrnA, located downstream from a single copy of the murA gene, which encodes an enzyme (EC 2.5.1.7) important for peptidoglycan synthesis. The rrnA operon has a promoter, P1(A), located within the coding region of murA near the 3′ end. Samples of RNA were isolated from Mycobacterium tuberculosis at different stages of the growth cycle and from M. smegmatis grown under different conditions. RNase protection assays were used to investigate transcripts of both murA and rrnA. Transcription of murA was found to continue into the 16S rRNA gene, as if murA and rrnA form a hybrid (protein coding-rRNA coding) operon. During the growth of M. tuberculosis, the hybrid operon contributed approximately 2% to total pre-rRNA. Analysis of M. smegmatis RNA revealed that the level of murA RNA depended on the growth rate, and that the patterns of expression during the growth cycle were different for murA and rrnA. M. smegmatis has a second rRNA operon, rrnB, located downstream from a single copy of the tyrS gene, encoding tyro-syl-tRNA synthetase. Transcription of tyrS was found to continue into the 16S rRNA gene rrnB. The hybrid tyrS-rrnB operon contributed 0.2% to 0.6% to rrnB transcripts. The pattern of tyrS expression during the growth cycle matched the pattern of rrnB expression, reflecting the essential role of tyrS and rRNA in protein biosynthesis.
AB - All mycobacteria studied to date have an rRNA operon, designated rrnA, located downstream from a single copy of the murA gene, which encodes an enzyme (EC 2.5.1.7) important for peptidoglycan synthesis. The rrnA operon has a promoter, P1(A), located within the coding region of murA near the 3′ end. Samples of RNA were isolated from Mycobacterium tuberculosis at different stages of the growth cycle and from M. smegmatis grown under different conditions. RNase protection assays were used to investigate transcripts of both murA and rrnA. Transcription of murA was found to continue into the 16S rRNA gene, as if murA and rrnA form a hybrid (protein coding-rRNA coding) operon. During the growth of M. tuberculosis, the hybrid operon contributed approximately 2% to total pre-rRNA. Analysis of M. smegmatis RNA revealed that the level of murA RNA depended on the growth rate, and that the patterns of expression during the growth cycle were different for murA and rrnA. M. smegmatis has a second rRNA operon, rrnB, located downstream from a single copy of the tyrS gene, encoding tyro-syl-tRNA synthetase. Transcription of tyrS was found to continue into the 16S rRNA gene rrnB. The hybrid tyrS-rrnB operon contributed 0.2% to 0.6% to rrnB transcripts. The pattern of tyrS expression during the growth cycle matched the pattern of rrnB expression, reflecting the essential role of tyrS and rRNA in protein biosynthesis.
UR - http://www.scopus.com/inward/record.url?scp=33748259436&partnerID=8YFLogxK
M3 - Artículo
SN - 0148-916X
VL - 67
SP - 523
JO - International Journal of Leprosy and Other Mycobacterial Diseases
JF - International Journal of Leprosy and Other Mycobacterial Diseases
IS - 4 SUPPL.
ER -