Molecular cloning of Chinese hamster 1q31 chromosomal fragile site DNA that is important to mdr1 gene amplification reveals a novel gene whose expression is associated with spermatocyte and adipocyte differentiation.

DNA amplification plays important roles in the development of drug resistance and tumor progression. One mechanism of DNA amplification involves the breakage-fusion-bridge (BFB) cycle. We previously reported that in Chinese hamster ovary (CHO) cell line, breakage at fragile site 1q31 was associated with mdr1 gene amplification through the BFB mechanism.

Role of the G protein-coupled receptor kinase site serine cluster in beta2-adrenergic receptor internalization, desensitization, and beta-arrestin translocation.

There is considerable evidence for the role of carboxyl-terminal serines 355, 356, and 364 in G protein-coupled receptor kinase (GRK)-mediated phosphorylation and desensitization of beta(2)-adrenergic receptors (beta(2)ARs). In this study we used receptors in which these serines were changed to alanines (SA3) or to aspartic acids (SD3) to determine the role of these sites in beta-arrestin-dependent beta(2)AR internalization and desensitization. Coupling efficiencies for epinephrine activation of adenylyl cyclase were similar in wild-type and mutant receptors, demonstrating that the SD3 mutant did not drive constitutive GRK desensitization.

Differential phosphorylation and dephosphorylation of beta2-adrenoceptor sites Ser262 and Ser355,356.

Activated beta2-adrenoceptors are rapidly desensitized by phosphorylation of Ser262 by protein kinase A (PKA) and of Ser355,356 by G-protein-coupled receptor kinase (GRK). We sought to determine whether the phosphorylation and subsequent dephosphorylation of these sites had similar kinetics and requirements for receptor endocytosis. The phosphorylation of the PKA and GRK sites were measured using antibodies that recognize phosphoserine 262 and phosphoserine 355,356.

Delayed mechanism for induction of gamma-glutamylcysteine synthetase heavy subunit mRNA stability by oxidative stress involving p38 mitogen-activated protein kinase signaling.

Expression of the gamma-glutamylcysteine synthetase heavy subunit (gamma-GCSh), which encodes the rate-limiting enzymes for glutathione biosynthesis, is regulated by many cytotoxic agents. Moreover, gamma-GCSh mRNA expression is elevated in colorectal cancer, but how gamma-GCSh expression is regulated is not completely understood. By using actinomycin D, which inhibits new RNA synthesis, we showed that treatment of human colorectal cancer cells with the prooxidant sulindac increased the half-life of gamma-GCSh mRNA.

Rab11 regulates the recycling and lysosome targeting of beta2-adrenergic receptors.

The pericentriolar recycling endosome (RE) may be an alternative compartment through which some beta2-adrenergic receptors (beta2ARs) recycle from early endosomes to the cell surface during prolonged exposure to agonist. For the transferrin receptor, CXCR2, and the M4-muscarinic acetylcholine receptor, trafficking through the RE and receptor recycling is regulated by the small GTPase rab11. The precise role of the RE and rab11 in regulating the cellular trafficking of the beta2AR is not understood.

Endosome sorting of beta 2-adrenoceptors is GRK5 independent.

1. We have investigated the role of G protein-coupled receptor kinase 5 (GRK5) in the regulation of endosome sorting of human beta(2)-adrenoceptors. 2.

The NucE and NucD lysis proteins are not essential for secretion of the Serratia marcescens extracellular nuclease.

The nuclease of Serratia marcescens is an extracellular protein encoded by the nucA gene. Pre-nuclease carries a typical 21-amino-acid N-terminal signal sequence that interacts with the Sec machinery to allow the translocation of nuclease to the periplasm. In Escherichia coli the nuclease remains in the periplasm; however, S.