Search results for "Protein Biosynthesis"
showing 10 items of 220 documents
Eukaryotic mRNA decay: methodologies, pathways, and links to other stages of gene expression.
2012
mRNA concentration depends on the balance between transcription and degradation rates. On both sides of the equilibrium, synthesis and degradation show, however, interesting differences that have conditioned the evolution of gene regulatory mechanisms. Here, we discuss recent genome-wide methods for determining mRNA half-lives in eukaryotes. We also review pre- and posttranscriptional regulons that coordinate the fate of functionally related mRNAs by using protein- or RNA-based trans factors. Some of these factors can regulate both transcription and decay rates, thereby maintaining proper mRNA homeostasis during eukaryotic cell life.
Amino acid activation in Ciona ovary and developing egg
1964
E stata studiata la attivazione di alcuni amini acidi negli ovociti nell'uovo vergine e nell'uovo fecondato diCiona intestinalis. L'andamento della attivazione della glicina e stato seguito sino alla neurulazione. Il quantitativo di amino acidi attivati e minimo nell'uovo vergine, esso aumenta rapidamente dopo la fecondazione. Durante la gastrulazione la attivazione della glicina raggiunge i valori maggiori.
Molecular events associated with glucose repression of invertase in Saccharomyces cerevisiae.
1986
When S. cerevisiae growing in the presence of glucose (repressive condition) was shifted to higher temperatures, invertase was secreted. This secretion required protein synthesis, but was independent of RNA formation (Mormeneo & Sentandreu 1982). In addition accumulation of invertasespecific messenger RNA occurred in the absence of protein synthesis but was expressed only after synthesis of protein. Invertase mRNA was continuously synthesized under repressive conditions and the levels of this mRNA were regulated by the presence of glucose. The hexose regulated the concentration of this mRNA at the level of transcription and/or by sensitization of this messenger RNA. The expression of the in…
Synthesis of undulin by rat liver fat-storing cells: Comparison with fibronectin and tenascin
1992
Abstract Fat-storing cells (FSCs) are known to synthesize various components of the hepatic extracellular matrix and thereby play an important role during liver fibrogenesis. The aim of our study was to investigate the synthesis of undulin, a recently described connective tissue protein belonging to the fibronectin—tenascin superfamily of glycoproteins, by fat-storing cells in primary culture. SDS-PAGE analysis of immunoprecipitates from cell layer lysates or media pulse-labeled with radioactive methionine revealed undulin-specific bands A (270 kDa), B1 (190 kDa), and B2 (180 kDa) after reduction. A single undulin-specific transcript was detected at about 7 kb. Undulin synthesized by cell-f…
Transfection analysis of expression of mRNA isoforms encoding the nuclear autoantigen La/SS-B
1997
Transcription of the gene encoding for the nuclear autoantigen La resulted in La mRNA isoforms. A promoter switching combined with an alternative splicing pathway replaced the exon 1 with the exon 1'. The exon 1' contained GC-rich regions and an oligo(U) tail of 23 uridine residues. Moreover, it encoded for three open reading frames upstream of the La protein reading frame. Despite this unusual structure, when exon 1' La mRNAs were expressed in transfected cells, both exon 1 and 1' La mRNAs were translated to La protein, whereas the upstream open reading frames of the exon 1' were not translated. In addition to full-length exon 1' La mRNAs 5'-shortened exon 1' La mRNAs were detected. The ex…
Translation of hepatitis B virus (HBV) surface proteins from the HBV pregenome and precore RNAs in Semliki Forest virus-driven expression.
2004
Hepatitis B virus (HBV) pregenome RNA (pgRNA) serves as a translation template for the HBV core (HBc) protein and viral polymerase (Pol). HBV precore RNA (pcRNA) directs the synthesis of the precore (preC) protein, a precursor of the hepatitis B e antigen (HBeAg). pgRNA and pcRNA were expressed in the Semliki Forest virus (SFV) expression system. Besides the HBc and preC proteins, there was revealed the synthesis of all three forms of HBV surface (HBs) proteins: long (LHBs), middle (MHBs) and short (SHBs), the start codons of which are located more than 1000 nt downstream of the HBc and preC start codons. Moreover, other HBV templates, such as 3′-truncated pgRNA lacking 3′ direct repeat and…
Sequence-Specific Repression of Cotranslational Translocation of the Hepatitis B Virus Envelope Proteins Coincides with Binding of Heat Shock Protein…
1997
AbstractThe large L envelope protein of the hepatitis B virus has the peculiar capacity to adopt two transmembrane topologies. The N-terminal preS domain of L initially remains in the cytosol while the S domain is cotranslationally inserted into the endoplasmic reticulum membrane. The preS region of about half of the L molecules is posttranslationally translocated to the lumenal space. We now demonstrate that the repression of cotranslational translocation of preS is conferred by a preS1-specific sequence. By analysis of L deletion mutants, the cytosolic anchorage determinant was mapped to amino acid sequence 70 to 94 of L. The intrinsic potential of this determinant to suppress cotranslati…
Chaperones Involved in Hepatitis B Virus Morphogenesis
1999
Little is known about host cell factors necessary for hepatitis B virus (HBV) assembly which involves envelopment of cytosolic nucleocapsids by the S, M and L transmembrane viral envelope proteins and subsequent budding into intraluminal cisternae. Central to virogenesis is the L protein that mediates hepatocyte receptor binding and envelopment of capsids. To serve these topologically conflicting roles, L protein exhibits an unusual dual membrane topology, disposing its N-terminal preS domain inside and outside of the virion lipid envelope. The mixed topology is achieved by posttranslational preS translocation of about half of the L protein molecules across a post-endoplasmic reticulum memb…
Mammalian BiP controls posttranslational ER translocation of the hepatitis B virus large envelope protein.
2008
AbstractThe hepatitis B virus L protein forms a dual topology in the endoplasmic reticulum (ER) via a process involving cotranslational membrane integration and subsequent posttranslational translocation of its preS subdomain. Here, we show that preS posttranslocation depends on the action of the ER chaperone BiP. To modulate the in vivo BiP activity, we designed an approach based on overexpressing its positive and negative regulators, ER-localized DnaJ-domain containing protein 4 (ERdj4) and BiP-associated protein (BAP), respectively. The feasibility of this approach was confirmed by demonstrating that BAP, but not ERdj4, destabilizes the L/BiP complex. Overexpressing BAP or ERdj4 inhibits…
Sequences in the 5′ Nontranslated Region of Hepatitis C Virus Required for RNA Replication
2001
ABSTRACT Sequences in the 5′ and 3′ termini of plus-strand RNA viruses harbor cis -acting elements important for efficient translation and replication. In case of the hepatitis C virus (HCV), a plus-strand RNA virus of the family Flaviviridae , a 341-nucleotide-long nontranslated region (NTR) is located at the 5′ end of the genome. This sequence contains an internal ribosome entry site (IRES) that is located downstream of an about 40-nucleotide-long sequence of unknown function. By using our recently developed HCV replicon system, we mapped and characterized the sequences in the 5′ NTR required for RNA replication. We show that deletions introduced into the 5′ terminal 40 nucleotides abolis…