Regulation of p14^ARF expression by HPV‐18 E6 variants

Abstract

A common causative agent for uterine cervical cancer is the human papillomavirus type 18 (HPV-18) which has three phylogenic variants: Asian-Amerindian, European, and African. Each variant shows significant molecular differences in the E6 gene. E6 oncoprotein is a negative regulator of tumor suppressor protein p53, hence, this oncoprotein indirectly regulates the expression of tumor-suppressor p14(ARF) . p14(ARF) and p16(INK4A) genes are overexpressed in--and have been proposed as markers for--HPV-related cervical cancer. In order to dissect the role of E6 on the regulation of p14(ARF) expression, separating it from that of other intervening factors, transfection of E6 variants to MCF-7 cells was performed, assessing cDNA transcript levels by RT-PCR, whereas p14(ARF) and p53 expression were evaluated by immunocytochemistry and Western blot. E6 transfected cells differentially expressed transcripts of two molecular forms: E6 and E6*. The ratio of these two forms varied with the transfected E6 variant. With the Asian-Amerindian variant, the ratio was E6 > E6*, whereas with the European and the African the ratio was E6* > E6. As expected with the E6* construct, E6* transcripts were solely observed. In addition, when E6 > E6* and p53 expression was low, p14(ARF) was high and when E6* > E6 and p53 expression was high, p14(ARF) was low. In conclusion, each E6 variant distinctively affects p53 levels and consequently p14(ARF) expression, finding that could be related with the differences in oncogenic effect of infection with the diverse high-risk HPV variants.

The Role of E6 Spliced Isoforms (E6*) in Human Papillomavirus-Induced Carcinogenesis

“…It has been reported that nucleotide changes within HPV18 E6 variant genes (Asian-Amerindian, European and African phylogenetic branches) result in different E6/E6*I splicing patterns in MCF-7 cells and cervical tumor biopsies. Interestingly, the cells and tumors harboring the Asian-Amerindian variant of E6 expressed higher levels of E6 than E6*I, while those with the African variant exhibited a higher proportion of E6*I [ 88 , 89 ]. Furthermore, European variants of HPV16 do not exhibit differences in E6/E6* splicing patterns [ 90 ].…”

Designing of CD8⁺ and CD8⁺-overlapped CD4⁺ epitope vaccine by targeting late and early proteins of human papillomavirus

“…62,63 systems biology-based virtual cancer pathway prediction and kinetics A literature survey was performed to collect the required information about the selected protein sequences to design and predict the peptides involved in biochemical pathways. [64][65][66][67][68][69][70][71][72][73][74] A mathematical and computational model of the entire HPV45 infection signaling pathway interacting with specific genes in the presence of peptides was developed and was visualized using CellDesigner v4.4 modeling tool. 75 Nodes in the pathway represented the entities, and edges represented connectivity of one node to another, which was closely related to each other.…”

“…In addition, the CAVPVTTRY 4-12 epitope of E4 protein was predicted to have binding affinity for HLA-(A*29, A*30, B*58, B*35) allotypes (Table 1C). Among the five epitopes of E6 protein, RTEVYQFAF [41][42][43][44][45][46][47][48][49] and YSRIRE-LRY [72][73][74][75][76][77][78][79][80] were predicted to have binding affinity for HLA-A*(32:01, 29:02) and HLA-B*58: 01 MHC class I alleles (Table 1D). Out of 13 MHC-binding E7 peptides (Table 1E), STLSFVCPW [93][94][95][96][97][98][99][100][101] (HLA-A*32:01, HLA-B*58:01, HLA-B*57:01), LQQLFLSTL [87][88][89][90][91][92][93][94][95] (HLA-A*02:06), and QLFLSTLSF [89][90][91][92][93][94][95][96]…”

“…Out of 13 MHC-binding E7 peptides (Table 1E), STLSFVCPW [93][94][95][96][97][98][99][100][101] (HLA-A*32:01, HLA-B*58:01, HLA-B*57:01), LQQLFLSTL [87][88][89][90][91][92][93][94][95] (HLA-A*02:06), and QLFLSTLSF [89][90][91][92][93][94][95][96][97] (HLA-B*15:02, HLA-B*15:01, HLA-A*32:01) were predicted to have a binding affinity of IC 50 <200 nm. Furthermore, three out of seven epitopes of L1 protein, such as HVEEYDLQF [51][52][53][54][55][56][57][58][59] , TLTAEVMSY [67][68][69][70][71][72][73][74][75] , and LTAEVMSYI [68][69]…”

“…. Among these, the LTAE-VMSYI[68][69][70][71][72][73][74][75][76] demonstrated interactions with six alleles, viz, HLA-A*(68:02, 02:06, 02:01), HLA-B*58: 01, and HLA-C*(12:03, 15:02). In addition, 12 out of 17 epitopes of L2 protein, KRASATDLY 10-18 , STSFTNPAF 154-162 , FSDPSIIEV 162-170 , LVTFDNPAY 248-256 , HSDFMDIIR 273-281 , QIGGRVHFY 312-320 , ATDLYKTCK[14][15][16][17][18][19][20][21][22] , STINKSFTY 362-370 , MPSTAASSY 377-385 , TSAWDVPIY 393-401 , PTNAAT-STY 420-428 , and QYYLWPWYY 435-443 , exhibited significant binding affinity for the HLA alleles.…”