Coordination between NF-kappaB family members p50 and p52 is essential for mediating LTbetaR signals in the development and organization of secondary lymphoid tissues.

Recent studies revealed that the lymphotoxin/lymphotoxin beta receptor (LT)/LTbetaR system activates the noncanonical nuclear factor-kappaB (NF-kappaB) signaling pathway involving I kappa B kinase 1/I kappa B kinase alpha (IKK1/IKKalpha) and NF-kappaB-inducing kinase (NIK) to direct processing of the nfkappab2 protein p100 to yield RelB:p52 complexes. Despite the biochemical evidence, LT-, RelB-, p52-deficient mice show discrepant phenotypes. We now demonstrate that p105/p50 also constitutes an important pathway for LTbetaR signaling.

Expression of two Escherichia coli acetyl-CoA carboxylase subunits is autoregulated.

Acetyl-CoA carboxylase (ACC) catalyzes the first step of fatty acid biosynthesis, the synthesis of malonyl-CoA from acetyl-CoA using ATP and bicarbonate. In Escherichia coli and most other bacteria, ACC is composed of four subunits encoded by accA, accB, accC, and accD. Prior work from this laboratory showed that the in vivo expression of the accBC operon had a strikingly nonlinear response to gene copy number (Li, S.

Never fat or gaunt.

Bacteria stringently regulate the synthesis of their membrane phospholipids, but the responsible regulatory mechanisms are incompletely understood. In this issue of Developmental Cell, a study reports negative regulation of the transcription of several genes of fatty acid and phospholipid synthesis plus identification of the regulatory protein.