Search

Abstract: Post-translational modifications of the histones are centrally involved in the regulation of all DNA-templated processes, including gene transcription, DNA replication, recombination, and repair. These modifications are often dynamic, and their removal is just as important as their addition in proper regulation of cellular functions. Although histone acetylation/deacetylation and histone methylation/demethylation are highly studied, the functions and regulation of histone ubiquitination and deubiquitination are less well understood. This review highlights our current understanding of how histone ubiquitination impacts gene transcription, DNA repair, and cell cycle progression, and stresses the importance of deubiquitinases to normal cellular functions as well as to disease states such as cancer. [Copyright &y& Elsevier]

Simple Summary: Increased levels of the Usp22 deubiquitinase have been observed in several types of human cancer, particularly highly aggressive, therapy-resistant tumors. However, the role of Usp22 overexpression in cancer etiology is not known. To address whether Usp22 overexpression is sufficient to induce tumors in vivo, we created a mouse that expresses high levels of Usp22 in all tissues beginning in embryogenesis through to adulthood. Analyses of these mice clearly show that while Usp22 overexpression alters several tumor-related signaling pathways and induces associated morphological changes such as hyperbranching of the mammary gland, Usp22 overexpression alone is not sufficient to induce tumorigenesis. These findings indicate that Usp22 likely enhances tumor formation and progression through cooperation with oncoproteins that exacerbate abnormal signal transduction. Usp22 overexpression is observed in several human cancers and is correlated with poor patient outcomes. The molecular basis underlying this correlation is not clear. Usp22 is the catalytic subunit of the deubiquitylation module in the SAGA histone-modifying complex, which regulates gene transcription. Our previous work demonstrated that the loss of Usp22 in mice leads to decreased expression of several components of receptor tyrosine kinase and TGFβ signaling pathways. To determine whether these pathways are upregulated when Usp22 is overexpressed, we created a mouse model that expresses high levels of Usp22 in all tissues. Phenotypic characterization of these mice revealed over-branching of the mammary glands in females. Transcriptomic analyses indicate the upregulation of key pathways involved in mammary gland branching in mammary epithelial cells derived from the Usp22-overexpressing mice, including estrogen receptor, ERK/MAPK, and TGFβ signaling. However, Usp22 overexpression did not lead to increased tumorigenesis in any tissue. Our findings indicate that elevated levels of Usp22 are not sufficient to induce tumors, but it may enhance signaling abnormalities associated with oncogenesis. [ABSTRACT FROM AUTHOR]