Regulation of expression of the region 3 promoter of the Escherichia coli K5 capsule gene cluster involves H-NS, SlyA, and a large 5' untranslated region.

Escherichia coli group 2 capsule gene clusters are temperature regulated, being expressed at 37 degrees C but not at 20 degrees C. Expression is regulated at the level of transcription by two convergent promoters, PR1 and PR3. In this paper, we show that regulation of transcription from PR3 involves a number of novel features including H-NS, SlyA, and a large 741-bp 5' untranslated region (UTR). H-NS represses transcription from PR3 at 20 degrees C and binds both 5' and 3' of the transcription start site. The 3' downstream regulatory element (DRE) was essential for temperature-dependent H-NS repression. At 37 degrees C, SlyA activates transcription independent of H-NS but maximal transcription requires H-NS. The UTR is present between the transcription start site and the first gene in the operon, kpsM. We demonstrate that the UTR, as well as containing the H-NS DRE, functions to moderate the extent of transcription that reaches kpsM and allows the binding of antitermination factor RfaH.

Effect of different upright sitting postures on spinal-pelvic curvature and trunk muscle activation in a pain-free population.

STUDY DESIGN: A normative within-subjects single-group study. OBJECTIVE: To compare spinal-pelvic curvature and trunk muscle activation in 2 upright sitting postures ("thoracic" and "lumbo-pelvic") and slump sitting in a pain-free population. SUMMARY OF BACKGROUND DATA: Clinical observations suggest that both upright and slump sitting postures can exacerbate low back pain. Little research has investigated the effects of different upright sitting postures on trunk muscle activation. METHODS: Spinal-pelvic curvature and surface electromyography of 6 trunk muscles were measured bilaterally in 2 upright (thoracic and lumbo-pelvic) sitting postures and slump sitting in 22 subjects. RESULTS: Thoracic, compared to lumbo-pelvic, upright sitting showed significantly greater thoracic extension (P < 0.001), with significantly less lumbar extension (P < 0.001) and anterior pelvic tilt (P = 0.03). Furthermore, there was significantly less superficial lumbar multifidus (P < 0.001) and internal oblique (P = 0.03) activity, with significantly higher thoracic erector spinae (P < 0.001) and external oblique (P = 0.04) activity in thoracic upright sitting. There was no significant difference in superficial lumbar multifidus activity between thoracic upright and slump sitting. CONCLUSIONS: Different upright sitting postures resulted in altered trunk muscle activation. Thoracic when compared to lumbo-pelvic upright sitting involved less coactivation of the local spinal muscles, with greater coactivation of the global muscles. These results highlight the importance of postural training specificity when the aim is to activate the lumbo-pelvic stabilizing muscles in subjects with back pain.