Poster abstracts
Poster number 129 submitted by Courtney Szyjka
Investigation of a novel role in transcriptional regulation of the trp operon by TRAP
Courtney Szyjka (Dept. Biological Sciences, SUNY at Buffalo), Natalie Merlino (Dept. Microbiology and Immunology, SUNY at Buffalo), Paul Gollnick (Dept. of Biological Sciences, SUNY at Buffalo)
Abstract:
Transcriptional regulation of the tryptophan (trp) biosynthetic operon in Bacillus subtilis is controlled by the trp RNA-binding attenuator protein (TRAP). Regulation of this operon was initially described as involving two competing RNA structures present in the leader region upstream of the first gene in the operon. Formation of these structures, designated as the anti-terminator and terminator, is mutually exclusive due to shared bases. In the presence of excess tryptophan, TRAP binds to 11 (G/U)AG repeats in the trp leader region RNA and prevents anti-terminator formation, allowing formation of the terminator and thus the trp genes are not transcribed. In limiting tryptophan conditions, TRAP does not bind and the trp genes are transcribed and translated to produce the tryptophan biosynthesis enzymes. Recent work has shown that, in vivo, the terminator structure isn’t required for transcription termination in the presence of tryptophan, indicating that TRAP may have a more direct role in transcription termination. Through a genetic selection, a TRAP mutant was isolated that is capable of binding RNA and tryptophan at wild-type (WT) levels, but does not terminate transcription. In vitro transcription analysis with B. subtilis RNA polymerase (RNAP) of TRAP proteins from a variety of bacterial species showed a trend of WT levels of termination if TRAP contained an acidic residue at position 60, but not if there was a basic residue in this position. To test the hypothesis that TRAP interacts directly with RNAP to induce termination, we performed label transfer experiments. Our data indicate that TRAP may interact with the alpha subunit of RNAP, a subunit known to have many interactions with transcriptional regulator proteins.
Keywords: transcription, gene regulation