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Proteomics analysis of protein expression and specific protein oxidation in human papillomavirus transformed keratinocytes upon UVB irradiation.

ABSTRACT: Increasing evidence supports the role of oxidative stress in cancer development. Ultraviolet (UV) irradiation is one of the major sources of oxidative stress through the generation of reactive oxygen species (ROS). Besides the physiological function of ROS in cellular homeostasis, accumulating reports suggest that ROS are involved in all stages of multistep cancer development. In order to investigate the involvement of oxidative damage into the mechanisms of tumour progression, we used a parallel proteomic approach to analyse the protein expression profile and to identify oxidatively modified proteins in human papillomavirus (HPV)-transformed keratinocytes (HK-168 cells) upon ultraviolet B (UVB) exposure. The HK-168 cells were obtained from normal human epidermal keratinocytes transfected with the whole genome of the high-risk HPV type 16, unanimously recognized as an etiological agent of cervical carcinoma. Because of its year-long latency, this tumour offers a convenient model to study the role of environmental concurring agents in the multistep malignant progression. By the protein expression profile, we identified 21 proteins that showed different expression levels in HK-168 cells treated with UVB in comparison with untreated cells. Focusing on the oxidative modifications occurring at the protein level, we identified five proteins that showed elevated protein carbonyls levels: alpha-enolase, heat shock protein 75, annexin 2, elongation factor Tu and elongation factor gamma. Our results indicate that UVB-induced oxidative stress perturbs the normal redox balance and shifts HPV-transformed keratinocytes into a state in which the carbonylation of specific proteins is systematically induced. We suggest that UVB-induced modulation of protein expression combined with oxidative modification lead to protein dysfunction that might contribute to the malignant progression of transformed cells.

SUBMITTER: Perluigi M

PROVIDER: S-EPMC6512374 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Human papillomaviruses (HPVs) replicate in the cutaneous and mucosal epithelia, and the infectious cycle is synchronous with the differentiation program of the host keratinocytes. The virus initially infects dividing cells in the lower layers of the epithelium, where it establishes a persistent infection. The viral genome is maintained as a low-copy-number, extrachromosomal element in these proliferating cells but switches to the late stage of the life cycle in differentiated cells. The cellular chromatin adaptor protein Brd4 is involved in several stages and processes of the viral life cycle. In concert with the viral transcriptional regulator E2, Brd4 can repress transcription from the early viral promoter. Brd4 and E2 form a complex with the viral genome that associates with host chromosomes to partition the viral genome in dividing cells; Brd4 also localizes to active sites of productive HPV DNA replication. However, because of the difficulties in producing HPV viral particles, the role of Brd4 in modulating viral transcription and replication at the initial stage of infection is unclear. In this study, we have used an HPV18 quasivirus-based genome delivery system to assess the role of Brd4 in the initial infectivity of primary human keratinocytes. We show that, upon infection of primary human keratinocytes with HPV18 quasivirus, Brd4 activates viral transcription and replication. Furthermore, this activation is independent of the functional interaction between Brd4 and the HPV18 E2 protein.ImportanceHPVs lack encapsidated proteins and so rely exquisitely on host cellular factors to initiate their gene expression programs in newly infected cells. Brd4 is an important cellular chromatin adaptor molecule that normally activates host transcription initiation and elongation. In this study, we further optimize and utilize a quasivirus infection system to show that Brd4 activates HPV18 transcription at early stages of infection. HPVs are important human pathogens causing a wide range of cutaneous and tumorigenic morbidities. Therefore, specifically targeting this protein could provide a new target of therapeutic prevention of establishment of HPV infections.

Project description:Dr. Liu's research group is interested in studying the expression and functions of galectin-3, -7 and -12, in particular the roles of these proteins in inflammation and neoplasm. Members of the galectin family are known to participate in cellular homeostasis by modulating cell growth, controlling cell cycle progression, and inducing or inhibiting apoptosis. It is known that some galectins have similar functions. However, it is not fully understood whether they work cooperatively or not. As the outermost barrier of the body, skin is directly and frequently exposed to a prooxidative environment, including solar ultraviolet A (UVA), ultraviolet B (UVB) radiation, and air pollution. Several reports have shown that exposure of cells to UV increase or decrease the levels of galectins. For example, the amounts of galectin-7 mRNA and protein are increased rapidly after UVB irradiation of keratinocytes (Proc. Natl. Acad. Sci. USA 1999; 96:11329-34). Heat shock and subculturing decrease, while alkylating agents and UV-light increase galectin-3 (Cell Physiol Biochem 2000; 10:149-58). To analyze the change of all galectin gene expression profiles after UVB irradiation and to determine the presence or absence of coordinate regulation, we analyzed the gene expression profiles of keratinocytes exposed to UVB. Normal human epidermal keratinocytes (NHEK) were irradiated with 200 J/m2 of UVB. Total RNA will be extracted at 0, 6, 12 and 24 h after irradiation (duplicate) for analysis on the Glyco gene chip. Several reports have shown that exposure to UV light can regulate levels of galectin in skin. This study seeks to analyze the changes in all galectin gene expression profiles post-UVB irradiation to determine the presence or absence of coordinate regulation. In this study, normal human keratinocytes were irradiated with 200J/m2 of UVB. Total RNA was extracted at 0, 6, 12, and 24-hour post irradiation time points, in duplicate. Samples were hybridized and analyzed using the GLYCOv2 array.

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Proteomics analysis of protein expression and specific protein oxidation in human papillomavirus transformed keratinocytes upon UVB irradiation.

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