Validation and functional characterization of HJURP (Holliday Junction Recognition Protein) isoforms in astrocytoma cells

• Grant number: 22/09066-3
• Support Opportunities: Regular Research Grants
• Start date: November 01, 2022
• End date: April 30, 2025
• Field of knowledge: Biological Sciences - Morphology - Cytology and Cell Biology
• Principal Investigator: Valeria Valente
• Grantee: Valeria Valente
• Host Institution: Faculdade de Ciências Farmacêuticas (FCFAR). Universidade Estadual Paulista (UNESP). Campus de Araraquara. Araraquara , SP, Brazil
• Associated researchers: Patrick da Silva ; Rodolfo Bortolozo Serafim ; Wilson Araújo da Silva Junior

Abstract

Our group has demonstrated that HJURP is highly overexpressed in astrocytoma and is strongly correlated with worse prognosis of patients. HJURP is extensively characterized by loading CENP-A into the centromeres, and we also know from data of previous project that it is enrolled in DNA repair, radioresistance and confers proliferation capacity to astrocytoma cell lines. All the functions described for this protein were based on studies made with HJURP-A, the canonical isoform, but there are sequences deposited in the GenBank indicating the existence of 3 transcriptional variants (NM_018410.5, NM_001282962.1 e NM_001282963.1). The transcript variants (HJURP-2 and -3) present exon-skipping and encode hypothetical proteins (HJURP-B and -C) excluding phosphorylation sites already validated for HJURP-A. We underscore the S123 site, which is predicted as a CK2 (Casein Kinase 2) target. CK2 is involved in the control of DNA damage signaling and repair mechanisms. Recently, our group has experimentally verified the existence of these transcripts and found that the variants are differentially expressed during astrocytoma progression and in non-tumor brain tissues. In addition, HJURP-1 silencing did not affect the viability of astrocytoma cell lines, as occurs when all variants are silenced simultaneously. These results indicated that the HJURP-B and HJURP-C are indeed functional and can compensate for the lack of HJURP-A, at least partially. However, regulatory specificities might allow their action in different cellular processes or contexts, justifying the regulated production. Therefore, here we propose to characterize the molecular functions of HJURP isoforms in astrocytoma cells, pursuing to understand the mechanisms underlying the complexity of functions already known for HJURP. We will first obtain cells overexpressing HJURP-2 or HJURP-3 and proceed with a series of experiments to assess the involvement of each isoform in the maintenance of the centromeric chromatin and global chromatin structure, proliferation control, DNA damage signaling and repair, acquisition of radio-resistance etc. Therefore, we believe this study can greatly contribute to clarify the complexity of functions HJURP exerts and the roles of distinct isoforms in astrocytoma progression, which is especially relevant when considering the potential HJURP presents as a new therapeutic target for cancer. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

SERAFIM, RODOLFO B.; CARDOSO, CIBELE; STORTI, CAMILA B.; DA SILVA, PATRICK; QI, HONGYUN; PARASURAM, RAMYA; NAVEGANTE, GEOVANA; PERON, JEAN PIERRE S.; SILVA, WILSON A.; ESPREAFICO, ENILZA M.; et al. HJURP is recruited to double-strand break sites and facilitates DNA repair by promoting chromatin reorganization. Oncogene, v. 43, n. 11, p. 17-pg., 2024-01-26. (13/13465-1, 13/08135-2, 22/09066-3, 21/10032-3, 18/05018-9, 14/18189-5)