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Proteins that regulate transcription can do so either via direct contact with RNA Polymerase or through indirect interactions facilitated by adaptors, mediators, histone-modifying proteins, and nucleosome remodelers. Direct interactions to activate transcription is seen in bacteria as well as in some eukaryotic genes. In these cases, upstream activation sequences are adjacent to the promoters, and the activator proteins interact directly with the transcriptional machinery. For example, in...
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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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DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart,...
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The histone proteins in the nucleosomes are post-translationally modified (PTM) to increase or decrease access to DNA. The commonly observed PTMs are methylation, acetylation, phosphorylation, and ubiquitination of lysine amino acids in the histone H3 tail region. These histone modifications have specific meaning for the cell. Hence, they are called "histone code". The protein complex involved in histone modification is termed as "reader-writer" complex.
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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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DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
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[Poly(ADP-Ribose) Polymerases 1 and 2: Classical Functions and Interaction with New Histone Poly(ADP-Ribosyl)ation

T A Kurgina1, O I Lavrik1,2,3

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Molekuliarnaia Biologiia
|March 31, 2023
PubMed
Summary

Poly(ADP-ribose) (PAR) synthesis by PARP enzymes is crucial for DNA repair. A new protein, HPF1, modulates PARP1/2 activity, impacting histone modifications and cellular processes.

Keywords:
HPF1PARP1PARP2PARylationhistonespoly(ADP-ribose)poly(ADP-ribosyl)ation

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Area of Science:

  • Molecular Biology
  • Biochemistry

Context:

  • Poly(ADP-ribose) (PAR) is a critical post-translational modification involved in DNA repair.
  • Poly(ADP-ribose)polymerase (PARP) enzymes, particularly PARP1 and PARP2, synthesize PAR using nicotinamide adenine dinucleotide (NAD+).
  • PARP1 and PARP2 are key nuclear proteins regulating DNA repair and are promising chemotherapy targets.

Purpose:

  • To review the discovery and classical mechanisms of PARylation in higher eukaryotes.
  • To elucidate the role of the novel histone PARylation factor (HPF1) in modulating PARP1/2 activity.
  • To explore the interaction mechanism between HPF1 and PARP1/2.

Summary:

  • PAR is synthesized by PARP enzymes, crucial for DNA repair and other cellular processes.
  • Histone PARylation factor 1 (HPF1) forms a joint active site with PARP1/2, modulating their activity.
  • HPF1 facilitates histone modification at serine residues, representing a new regulatory mechanism in PARylation.

Impact:

  • Understanding HPF1's role provides insights into DNA repair pathways.
  • This research highlights PARP1/2 and HPF1 as potential targets for novel cancer therapies.
  • The findings advance the comprehension of post-translational modifications and their regulation.