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Related Concept Videos

Directionality of Nuclear Transport01:42

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Ras-related nuclear protein or Ran is a small G protein that cycles between its GTP and GDP bound states. Ran specific regulators, a Ran GTPase Activating Protein or RanGAP present in the cytosol and a Ran guanine nucleotide exchange factor or RanGEF present inside the nucleus regulate GTP/GDP exchange. A high concentration of GTP inside the cells, in addition to this asymmetric distribution of  Ran-specific regulators, leads to a higher RanGTP concentration inside the nucleus. This...
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Proteins targeted to the nucleus carry short stretches of amino acid sequences called the nuclear localization signal or NLS. Classical nuclear localization signals are of two types: monopartite and bipartite NLS. Monopartite classical NLS (cNLS) consists of a single cluster of 4-8 amino acids. Bipartite cNLS consists of two clusters of  2-3 amino acids and a 9-12 residue long proline-rich linker bridging the two clusters. Signal clusters are rich in positively charged amino acids such as...
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During most eukaryotic translation processes, the small 40S ribosome subunit scans an mRNA from its 5' end until it encounters the first start AUG codon. The large 60S ribosomal subunit then joins the smaller one to initiate protein synthesis. The location of the translation initiation is largely determined by the nucleotides near the start codon as there may be multiple translation initiation sites present on the mRNA.  Marilyn Kozak discovered that the sequence RCCAUGG (where R...
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Eukaryotic RNA Polymerases00:58

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RNA Polymerase (RNAP) is conserved in all animals, with bacterial, archaeal, and eukaryotic RNAPs sharing significant sequence, structural, and functional similarities. Among the three eukaryotic RNAPs, RNA Polymerase II is most similar to bacterial RNAP in terms of both structural organization and folding topologies of the enzyme subunits. However, these similarities are not reflected in their mechanism of action.
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Bacterial RNA Polymerase00:43

Bacterial RNA Polymerase

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Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. The multisubunit structure of the bacterial RNAP helps the enzyme to maintain catalytic function, facilitate assembly, interact with DNA and RNA, and self-regulate its activity.
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Transcription Initiation01:47

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Initiation is the first step of transcription in eukaryotes. Prokaryotic RNA Polymerase (RNAP) can bind to the template DNA and start transcribing. On the other hand, transcription in eukaryotes requires additional proteins, called transcription factors, to first bind to the promoter region in the DNA template. This binding helps recruit the specific RNAP that can assemble on the DNA and start transcription.
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Affinity Purification of Influenza Virus Ribonucleoprotein Complexes from the Chromatin of Infected Cells
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Structural insights into Influenza A virus RNA polymerase PB1 binding to nuclear import host factor RanBP5.

Tomomi Uchikubo-Kamo1, Naito Ishimoto1, Haruka Umezawa1

  • 1Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, Tsurumi, Yokohama, 230-0045, Japan.

Biochemical and Biophysical Research Communications
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Summary

Influenza A virus RNA polymerase subunits are imported into the nucleus via host factor Ran binding protein 5 (RanBP5). Structural analysis reveals how PB1 NLS domain interacts with RanBP5, aiding drug discovery.

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Related Experiment Videos

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Multi-target Parallel Processing Approach for Gene-to-structure Determination of the Influenza Polymerase PB2 Subunit
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Area of Science:

  • Virology
  • Structural Biology
  • Molecular Biology

Background:

  • Influenza A virus RNA polymerase subunits (PB1, PA, PB2) are essential for viral transcription and replication within the host cell nucleus.
  • Nuclear import of these subunits is a critical step during viral infection, but the underlying molecular mechanisms involving host factors are not fully understood.
  • Existing models suggest PB1 and PA dimerize and are imported by Ran binding protein 5 (RanBP5), with PB2 imported separately.

Purpose of the Study:

  • To elucidate the structural basis of nuclear import for influenza A virus RNA polymerase subunits.
  • To investigate the interaction between Ran binding protein 5 (RanBP5) and the nuclear localization signal (NLS) domain of the PB1 subunit.
  • To identify key amino acid residues involved in the complex formation between RanBP5 and PB1.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) was employed to determine the structure of the RanBP5 and PB1 NLS domain complex at 3.2 Å resolution.
  • Biochemical analyses, including mutant studies, were performed to identify critical amino acid sites mediating complex binding.

Main Results:

  • The cryo-EM structure revealed that the PB1 NLS domain lacks secondary structure and adopts a 'wrapped' conformation when interacting with RanBP5.
  • Biochemical data identified specific amino acid residues crucial for the binding interaction between RanBP5 and the PB1 NLS domain.
  • These findings provide atomic-level insights into the host-pathogen interaction during viral nuclear import.

Conclusions:

  • The study suggests a stepwise assembly mechanism for influenza virus structural components, regulated by nuclear import pathways and host factor interactions.
  • The identified interaction interface between RanBP5 and PB1 is a potential target for antiviral drug development.
  • Understanding these host-pathogen interactions is crucial for developing novel therapeutic strategies against influenza A virus.