PubMed Health⌕ Search

Biomedical subjects

P H Olsen

Publications and source records attributed to P H Olsen.

4 recordsLinked to original sources
PubMed1999

The lin-4 regulatory RNA controls developmental timing in Caenorhabditis elegans by blocking LIN-14 protein synthesis after the initiation of translation.

lin-4 encodes a small RNA that is complementary to sequences in the 3' untranslated region (UTR) of lin-14 mRNA and that acts to developmentally repress the accumulation of LIN-14 protein. This repression is essential for the proper timing of numerous events of Caenorhabditis elegans larval development. We have investigated the mechanism of lin-4 RNA action by examining the fate of lin-14 mRNA in vivo during the time that lin-4 RNA is expressed. Our results indicate that the rate of synthesis of lin-14 mRNA, its state of polyadenylation, its abundance in the cytoplasmic fraction, and its polysomal sedimentation profile do not change in response to the accumulation of lin-4 RNA. Our results indicate that association of lin-4 RNA with the 3' UTR of lin-14 mRNA permits normal biogenesis of lin-14 mRNA, and normal translational initiation, but inhibits step(s) thereafter, such as translational elongation and/or the release of stable LIN-14 protein.

3' Untranslated Regions↗
PubMed1992

Ca2+ dependence of the interactions between protein C, thrombin, and the elastase fragment of thrombomodulin. Analysis by ultracentrifugation.

The two-way and three-way interactions among active-site-blocked bovine thrombin, bovine protein C, and the elastase fragment of rabbit thrombomodulin (elTM) were examined by analytical ultracentrifugation at 23.3 degrees C in 100 mM NaCl, 50 mM Tris (pH 7.65), and 1 mM benzamidine, in the presence of 0 to 5 mM calcium chloride. Thrombin and elTM form a tight (Kd less than 10(-8) M) 1:1 complex in the absence of Ca2+ that weakens with the addition of Ca2+ (Kd approximately 4 microM in 5 mM Ca2+). Without Ca2+, thrombin and protein C form a 1:1 complex (Kd approximately 1 microM) and what appears to be a 1:2 thrombin-protein C complex. The Kd for the 1:1 complex weakens over 100-fold in 5 mM CaCl2. Protein C and elTM form a Ca(2+)-independent 1:1 complex (Kd approximately 80 microM). Nearly identical binding to thrombin and elTM is observed when active-site-blocked activated bovine protein C is substituted for protein C. Thrombin inhibited by diisopropyl fluorophosphate and thrombin inhibited by a tripeptide chloromethyl ketone exhibited identical behavior in binding experiments, suggesting that the accessibility of protein C to the substrate recognition cleft of these two forms of thrombin is nearly equal. Human protein C binds with lower affinity than bovine protein C. Ternary mixtures also were examined. Protein C, elTM, and thrombin form a 1:1:1 complex which dissociates with increasing [Ca2+]. In the absence of Ca2+, protein C binds to the elTM-thrombin complex with an apparent Kd approximately 1 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗