Influence of ERF3A/GSPT1 gene expression on susceptibility to carcinogenesis

• Author(s): Vacas, Joana Malta, 1977-
• Date: 2009
• Persistent ID: http://hdl.handle.net/10451/1648
• Origin: Repositório da Universidade de Lisboa
• Subject(s): Cancro; Expansão GGC; Expressão genética; Biologia molecular; Teses de doutoramento - 2009
• Document Type: Doctoral thesis
• Language: English
• Advisor(s): Brito, Rui Miguel Duque de, 1969-; Coelho, Maria Manuela, 1954-
• Contributor(s): Repositório da Universidade de Lisboa

Description

Tese de doutoramento, Biologia (Biologia Molecular), Universidade de Lisboa, Faculdade de Ciências, 2009

The eukaryotic release factor 3 (eRF3) associates with eRF1 in a complex that mediatestranslation termination. In addition to its roles in translation, eRF3 is also involved in cell cycleregulation, apoptosis and cytoskeleton assemble. Human eRF3 has two distinct isoforms, eRF3aand eRF3b, encoded by eRF3a/GSPT1 and eRF3b/GSPT2 genes.eRF3a/GSPT1 contains a stable (GGC)n expansion coding for proteins with different N-terminalextremities. We identified five alleles encoding 7, 9, 10, 11 and 12 GGC repeats in thePortuguese population, being the 10GGC allele the most frequent (F= 68.5% in the controlpopulation). The longer allele (12GGC) was exclusively detected in 5.1% of the cancer patients(N=411) with an allele frequency of 3%, corresponding to a 12-fold increased cancer risk.Our results show that the mRNA levels of eRF3a/GSPT1 are overexpressed in a significantproportion of different types of cancer. Moreover, the transcript levels of eRF3a/GSPT1 showvariation between alleles, being the 12GGC allele significantly overexpressed (p<0.001). Thelevels of eRF3a/GSPT1 transcription are not associated with eRF3a/GSPT1 amplification neitherwith the methylation pattern of the GGC expansion region.Using an in vivo assay for readthrough efficiency, we do not detect any difference in the activityof the eRF3a proteins encoded by the five different eRF3a/GSPT1 alleles. Also, no differences inthe levels of apoptosis and proliferation rates were found between cells lines. Finally, using acytokinesis-block micronucleos assay, we show that cells with the longer alleles have higherfrequencies of MN, which is probably a result of defects in mitotic spindle formation.Although the connection between eRF3a/GSPT1 and tumorigenesis is not completely elucidated,our data suggests that the presence of the 12GGC allele provides a novel risk marker for cancer.Taken together, our results show that eRF3a should be considered as a potential proto-oncogene

Fundação Para a Ciência e a Tecnologia (SFRH/BD/21468/2005, projects POCTI/MGI/40071/2001 and PTDC/SAU-GMG/67031/2006)