The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform

A. Lorena Passarelli - One of the best experts on this subject based on the ideXlab platform.

  • Baculovirus RNA Polymerase: Activities, composition, and evolution
    Virologica Sinica, 2007
    Co-Authors: A. Lorena Passarelli
    Abstract:

    Baculoviruses are the only nuclear replicating DNA-containing viruses that encode their own DNA-directed RNA Polymerase (RNAP). The baculovirus RNAP is specific for the transcription of genes expressed after virus DNA replication. It is composed of four subunits, making it the simplest multisubunit RNAP known. Two subunits contain motifs found at the catalytic center of other RNAPs and a third has capping enzyme functions. The function of the fourth subunit is not known. Structural studies on this unique RNAP will provide new insights into the functions of this enzyme and the regulation of viral genes and may be instrumental to optimize the baculovirus gene expression system.

  • Functional dissection of the baculovirus late expression factor-8 gene: sequence requirements for late gene promoter activation
    Journal of General Virology, 2003
    Co-Authors: Jane S. Titterington, A. Lorena Passarelli
    Abstract:

    The late expression factor-8 gene (lef-8) of Autographa californica M nucleopolyhedrovirus encodes the largest subunit of the virally encoded DNA-directed RNA Polymerase specific for the transcription of late and very late viral genes. The sequence of lef-8 predicts a C-terminal motif of 13 amino acids that is conserved in other Polymerases. Detailed mutagenesis throughout lef-8 was performed, including this C-terminal motif, to define sequences required for late promoter activation. It was found that the conserved C-terminal motif was critical for late gene expression. In addition, regions throughout the entire lef-8-encoding sequence were important for optimal function, suggesting complex protein–protein and protein–DNA interrelationships in the late gene-specific viral transcriptosome.

Linda A. Guarino - One of the best experts on this subject based on the ideXlab platform.

  • Processing of baculovirus late and very late mRNAs
    Virologica Sinica, 2007
    Co-Authors: Linda A. Guarino
    Abstract:

    Baculoviruses encode a DNA-directed RNA Polymerase that is evolutionarily divergent from cellular Polymerases. This RNA Polymerase is a multifunctional complex that has the ability to recognize late promoters, transcribe linked genes, and process transcripts at both the 5′ and 3′ ends. The LEF-4 subunit of the viral RNA Polymerase is the mRNA capping enzyme, with both RNA triphosphatase and guanylyltransferase activities. Conversion to cap 1 structures is mediated by the viral enzyme MTase1 and another as yet unidentified methyltransferase. Termination is an intrinsic property of the viral RNA Polymerase and occurs at oligoU rich sequences. Polyadenylation of the released transcripts is also a function of the viral RNA Polymerase. Thus, although viral mRNAs resemble host messages with respect to their 5′ and 3′ end structures, the processing is mediated by viral enzymes and, in the case of the 3′ ends, by mechanisms that differ from the host cell.

  • A virus-encoded RNA Polymerase purified from baculovirus-infected cells
    Journal of Virology, 1998
    Co-Authors: Linda A. Guarino, Bin Xu, Wen Dong
    Abstract:

    A DNA-dependent RNA Polymerase was purified to homogeneity, starting from insect cells infected with the baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV). The purified Polymerase supported accurate and specific transcription from late and very late promoters but was not active on viral early promoters. Thus, promoter recognition is an integral function of the purified enzyme. The purified RNA Polymerase was composed of only four equimolar subunits, which makes it the simplest DNA-directed RNA Polymerase from a eukaryotic source described so far. Amino-terminal protein sequencing, peptide fingerprinting, and immunochemical analyses were used to identify the four subunits, all of which are virus encoded. Overexpression of the four viral proteins (LEF-8, LEF-4, LEF-9, and p47) in baculovirus-infected cells resulted in a significant increase in the levels of RNA Polymerase produced in the infected cells. Thus, the overexpression data are consistent with our identification of the RNA Polymerase subunits.

Mitiko Go - One of the best experts on this subject based on the ideXlab platform.

  • Preparation of S-Protected Cysteine-Containing Peptide Thioester and Its Use for the Synthesis of the BaRNAse-Like Domain in DNA-directed RNA Polymerase II of Saccharomyces cerevisiae
    Bulletin of the Chemical Society of Japan, 1995
    Co-Authors: Hironobu Hojo, Mitiko Go, Shoko Yoshimura, Saburo Aimoto
    Abstract:

    The BaRNAse-like Domain in DNA-directed RNA Polymerase II of Saccharomyces cerevisiae containing three cysteine residues was synthesized by a thioester method. A partially-protected cysteine-containing peptide thioester was prepared via a peptide obtained by a solid-phase method using 3-nitro-2-pyridinesulfenyl amino acid derivatives. Four peptide segments covering 112 amino acid residues of the baRNAse-like domain were condensed from the C-terminal to the N-terminal one by one in the presence of silver ions and N-hydroxysuccinimide to give a full sequence peptide. RNAse activity of the synthetic domain could not be detected because of its extreme low solubility in the neutral buffer.

  • RNAse-like domain in DNA-directed RNA Polymerase II.
    Proceedings of the National Academy of Sciences of the United States of America, 1991
    Co-Authors: T. Shirai, Mitiko Go
    Abstract:

    Abstract DNA-directed RNA Polymerase is responsible for gene expression. Despite its importance, many details of its function and higher-order structure still remain unknown. We report here a local sequence similarity between the second largest subunit of RNA Polymerase II and bacterial RNAses Ba (baRNAse), Bi, and St. The most remarkable similarity is that the catalytic sites of the RNAses are shared with the eukaryotic RNA Polymerase II subunits of Drosophila melanogaster and Saccharomyces cerevisiae. Several amino acids conserved among the RNAses and the RNAse-like domains of the RNA Polymerase subunits are located in the neighborhood of the catalytic sites of baRNAse, whose three-dimensional structure has been resolved. This observation suggests the functional importance of the RNAse-like domain of the RNA Polymerase subunits and indicates that the RNAse-like domain may have RNAse activity. The location of the RNAse-like domain relative to the region necessary for RNA polymerization is similar to the relative proximity of 5'----3' or 3'----5' exonuclease and the region of Polymerase activity of DNA Polymerase I. The RNAse-like domain might work in proofreading, as in RNA-directed RNA Polymerase of influenza virus, or it may contribute to RNA binding through an unknown function.

Lin-woo Kang - One of the best experts on this subject based on the ideXlab platform.

  • Expression, crystallization and preliminary X-ray crystallographic analysis of DNA-directed RNA Polymerase subunit L from Thermococcus onnurineus NA1.
    Acta Crystallographica Section F-structural Biology and Crystallization Communications, 2014
    Co-Authors: Thien-hoang Ho, Myoung-ki Hong, Lin-woo Kang
    Abstract:

    RNA Polymerase (RNAP) plays a crucial role in gene expression in all organisms. It is a multiprotein complex that produces primary transcript RNA. Generally, the basal transcription apparatus in archaea is simpler than the eukaryotic RNA Polymerase II counterpart. To understand the structure and function of archaeal RNAP, the TON-0309 gene encoding DNA-directed RNA Polymerase subunit L (ToRNAP_L) from Thermococcus onnurineus NA1 was cloned and the protein was overexpressed in Escherichia coli, purified and crystallized. The purified protein was crystallized using the hanging-drop vapour-diffusion method and the crystal diffracted to 2.10 A resolution. The crystal belonged to the hexagonal space group P6122, with unit-cell parameters a = b = 42.3, c = 211.2 A. One molecule was present in the asymmetric unit, with a corresponding V M of 2.5 A3 Da−1 and a solvent content of 50.0%.

Junho Chung - One of the best experts on this subject based on the ideXlab platform.