Nonsense-mediated mRNA decay (NMD) represents a eukaryotic quality control pathway that recognizes and rapidly degrades transcripts harbouring nonsense mutations to limit accumulation of non-functional and potentially toxic truncated polypeptides. A critical component of the NMD machinery is UPF1, an RNA helicase whose ATPase activity is essential for NMD, but for which the precise function and...

Mutations in DAX1 [dosage-sensitive sex reversal-adrenal hypoplasia congenita (AHC) critical region on the X chromosome gene 1; NR0B1] cause X-linked AHC, a disease characterized by primary adrenal failure in infancy or childhood and reproductive abnormalities later in life. Most of these patients have nonsense or frameshift mutations that cause premature truncation of the DAX1 protein, thereby...

Unlike the situation in prokaryotes, most eukaryotic messenger RNAs contain a moderately long 5' untranslated region (UTR). Such leader sequences impose a burden on eukaryotic genes by providing substrate for the mutational origin of premature translation-initiation codons, which generally result in defective proteins. To gain an insight into the expansion of 5' UTRs in eukaryotic genomes, we p...

In phage P4, transcription of the left operon may occur from both the constitutive PLE promoter and the regulated PLL promoter, about 400 nucleotides upstream of PLE. A strong Rho-dependent termination site, timm, is located downstream of both promoters. When P4 immunity is expressed, transcription starting at PLE is efficiently terminated at timm, whereas transcription from PLL is immunity ins...

OBJECTIVES Haemostasis prevents blood loss following vascular injury. It depends on the unique concert of events involving platelets and specific blood proteins, known as coagulation factors. The clotting system requires precise regulation and coordinated reactions to maintain the integrity of the vasculature. Clotting insufficiency mostly occurs due to genetically inherited coagulation factor ...

A poliovirus type I (Mahoney strain) mutant was obtained by inserting three base pairs into an infectious cDNA clone. The extra amino acid encoded by the insertion was in the amino-terminal (protein 8) portion of the P2 segment of the polyprotein. The mutant virus makes small plaques on HeLa and monkey kidney (CV-1) cells at all temperatures. It lost the ability to mediate the selective inhibit...

MHC class I peptides are products of endogenous cellular protein degradation. Their prompt presentation, after rapid degradation of their newly synthesized source proteins, is needed to alert the immune system during pathogen infection. A possible source for such rapidly degrading proteins can be defective ribosome products (DRiPs), which include polypeptides produced as part of the pioneer rou...