The upstream region of the SP-B gene: intrinsic promoter activity and glucocorticoid responsiveness related to a new DNA-binding protein

Gene structure and promoter function of murine Munc18-2, a nonneuronal exocytic Sec1 homolog

Sec1 family proteins are regulators of diverse exocytic processes, from yeast to man. Three mammalian homologues, Munc18-1, -2, and -3 have been described. We have studied the structure and expression of the mouse Munc18-2 gene. The Munc18-2 gene comprises 19 exons whose sizes range from 50 to 158 bp, with a total gene size of approximately 11 kb. A single transcript of 2.1 kb is expressed in multiple non-neuronal murine tissues. Munc18-2 has a striking resemblance to Munc18-1 in structure despite only 60% sequence identity, suggesting a recent gene duplication event. Analysis of the region upstream of the transcription start site shows that Munc18-2 has a TATA-less promoter, with a consensus initiator (Inr) sequence at the start of transcription, several Sp1 binding sites, and strong promoter activity in RBL-2H3 mast cells. The region from +5 to -430 is more active than +5 to -800, suggesting upstream repressor elements.

Regulation and function of pulmonary surfactant protein B

Pulmonary surfactant, a complex mixture of phospholipids and specific associated proteins, reduces the surface tension at the air-liquid interface of the distal conducting airways and gas exchanging alveoli of the lung. Lipids, primarily neutral and phospholipids, compose approximately 90% of the surfactant complex. The remaining 10% of surfactant is composed of at least three surfactant-specific proteins, designated surfactant protein A (SP-A), SP-B, and SP-C. These proteins contribute to the formation, stabilization, and function of organized surfactant structures. This article briefly reviews the normal composition and function of pulmonary surfactant and specifically reviews the structure, function, and regulation of surfactant protein B (SP-B). The recent identification of neonates with refractory respiratory failure due to a genetic absence of SP-B and the study of transgenic mice in which SP-B gene expression has been ablated highlight the importance of the protein to surfactant function, synthesis, and metabolism and to the maintenance of lung function. Gene reconstitution experiments in vitro and in SP-B-deficient transgenic mice suggest specific functions for the amino and carboxyl terminal domains of the protein. SP-B deficiency is a potential target for gene therapy in human patients.