RPA2

What is RPA2 protein?

RPA2 gene (replication protein A2) is a protein coding gene which situated on the short arm of chromosome 1 at locus 1p35. This gene encodes a subunit of the heterotrimeric Replication Protein A (RPA) complex, which binds to single-stranded DNA (ssDNA), forming a nucleoprotein complex that plays an important role in DNA metabolism, being involved in DNA replication, repair, recombination, telomere maintenance, and co-ordinating the cellular response to DNA damage through activation of the ataxia telangiectasia and Rad3-related protein (ATR) kinase. The RPA complex protects single-stranded DNA from nucleases, prevents formation of secondary structures that would interfere with repair, and co-ordinates the recruitment and departure of different genome maintenance factors. The RPA2 protein is consisted of 270 amino acids and RPA2 molecular weight is approximately 29.2 kDa.

What is the function of RPA2 protein?

RPA2 Protein is A key subunit of Replication Protein A, which plays an important role in DNA replication, repair and recombination. The main functions of RPA2 include binding and protecting single-stranded DNA, promoting the activity of DNA polymerase, participating in the repair of DNA damage, and recognizing and processing DNA double-stranded breaks in homologous recombination. In addition, RPA2 may also be involved in the regulation of the cell cycle and the initiation of DNA replication, and is essential for maintaining genome stability and cell survival.

RPA2 related signaling pathway

When DNA damage occurs or during normal cellular processes like DNA replication, RPA2 recognizes single-stranded DNA (ssDNA) exposed by unwinding of the double helix. This recognition triggers a cascade of events: RPA2 recruits and activates other proteins such as Rad9, Hus1, and Rad1 (the 9-1-1 complex), which function in cell cycle checkpoints and DNA repair mechanisms. Additionally, it interacts with translesion synthesis polymerases to facilitate error-free repair over damaged templates. Furthermore, RPA2's interaction with ATR (Ataxia Telangiectasia and Rad3-related protein) kinase initiates the DNA damage response pathway, leading to phosphorylation of downstream effectors like p53 and Chk1/Chk2, crucial for cell cycle arrest and apoptosis if necessary. This intricate network ensures that cells can respond appropriately to DNA lesions, preserving genome integrity and preventing carcinogenesis.

RPA2 related diseases

The abnormal function of RPA2 protein is related to the occurrence and development of many diseases. RPA2 is involved in DNA replication, repair, and recombination, and abnormalities in RPA2 may affect these key cellular processes. RPA2 is associated with the occurrence of breast cancer, prostate cancer, lung cancer and other cancers, and its expression level in tumor tissues may be abnormally increased, affecting the course of the disease. In addition, RPA2 has been implicated in neurodegenerative diseases such as Huntington's disease and spinocerebellar ataxia type 1 (SCA1), where upregulated expression of RPA2 may be associated with disease-associated tandem CAG repeat instability. The genetic variation of RPA2 is also considered as a novel genetic factor in some telomere biological diseases. Overall, RPA2 plays a crucial role in maintaining genomic stability and preventing disease.

Fig1. Overexpression of RPA subunits or hyperphosphorylation of RPA2 may serve as a prognostic biomarker in tumor specimens. (Rositsa Dueva, 2020)

Bioapplications of RPA2

RPA2 has significant bioapplications, particularly in the field of cancer research and therapy. Its role in recognizing single-stranded DNA and facilitating DNA repair mechanisms makes it a potential target for developing drugs aimed at enhancing tumor suppression or improving the efficacy of radiotherapy and chemotherapy. By modulating RPA2 activity, researchers aim to sensitize cancer cells to DNA-damaging treatments while minimizing harm to normal cells. Additionally, understanding RPA2's involvement in genomic stability can lead to the development of diagnostic biomarkers for early detection of cancers and other genetic disorders. In summary, RPA2's critical functions in DNA metabolism offer promising avenues for advancing personalized medicine and improving clinical outcomes in oncology and genetic diseases.

Case Study 1: Yongqiang Lai, 2019

Replication Protein A (RPA) binds to single-stranded DNA and is essential for genome stability. The E3 ubiquitin ligase HERC2 regulates RPA-helicase complexes to suppress G-quadruplex DNA. However, the exact mechanism of HERC2 on RPA is unknown. Here, HERC2 induces phosphorylation and degradation of RPA2 by interacting with its C-terminal HECT domain. Ubiquitination of RPA2 is inhibited by HERC2 depletion but restored by reintroducing the C-terminal fragment of HERC2. ATR-mediated phosphorylation of RPA2 at Ser33, induced by low-level replication stress, is inhibited by HERC2 depletion. Conversely, cells lacking HERC2 catalytic residues have increased levels of Ser33-phosphorylated RPA2. HERC2-mediated ubiquitination of RPA2 is abolished by an ATR inhibitor, suggesting that ubiquitinated RPA2 is a phosphorylated subset. Functionally, HERC2 E3 activity is epistatic to RPA in suppressing G4, as shown by siRNA knockdown experiments.

Fig1. HeLa-shHERC2 cells were co-transfected with the indicated HERC2 fragments and St2-RPA2.

Fig2. HeLa-shHERC2 cells were co-transfected with St2-RPA2 and HA-ubiquitin.

Case Study 2: Wei Shi, 2010

Stalled DNA replication forks can lead to genomic instability, and homologous recombination (HR) repairs such DNA damage. Replication protein A (RPA) is central to DNA metabolism, but the significance of RPA2 hyperphosphorylation in response to DNA damage has been obscure. This study reveals that hyperphosphorylated RPA2 binds to ssDNA and Rad51 upon replication arrest induced by hydroxyurea (HU), and is vital for Rad51 recruitment and HR repair post-HU. However, this hyperphosphorylation is not needed for Rad51 focus formation after ionizing radiation (IR) or HR stimulated by I-Sce-I endonuclease. Furthermore, a non-phosphorylatable RPA2 mutant increases chromosomal aberrations post-HU, but not after IR, indicating that RPA2 hyperphosphorylation is crucial specifically for coping with replication stress, rather than IR-induced damage.

Fig3. Whole cell lysates were isolated from MCF7 cells that were mock treated or exposed to replication inhibitor.

Fig4. Colocalization of phosphorylated RPA2 with ssDNA.

RPA2 has several biochemical functions, for example, damaged DNA binding,enzyme binding,protein N-terminus binding. Some of the functions are cooperated with other proteins, some of the functions could acted by RPA2 itself. We selected most functions RPA2 had, and list some proteins which have the same functions with RPA2. You can find most of the proteins on our site.

RPA2 has direct interactions with proteins and molecules. Those interactions were detected by several methods such as yeast two hybrid, co-IP, pull-down and so on. We selected proteins and molecules interacted with RPA2 here. Most of them are supplied by our site. Hope this information will be useful for your research of RPA2.

RPA1;RPA3;SMARCAL1