NFX1-123 Increases hTERT Expression and Telomerase Activity Posttranscriptionally in Human Papillomavirus Type 16 E6 Keratinocytes
NFX1-123 Increases hTERT Expression and Telomerase Activity Posttranscriptionally in Human Papillomavirus Type 16 E6 Keratinocytes
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DOI：
10.1128/jvi.02556-08
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发表时间：
2009-07-01
影响因子：
5.4
通讯作者：
Galloway, Denise A.
中科院分区：
文献类型：
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作者：
Katzenellenbogen, Rachel A.;Vliet-Gregg, Portia;Galloway, Denise A.
高危型人乳头瘤病毒（HPV）E6蛋白通过转录激活端粒酶催化亚单位hTERT诱导端粒酶活性。HPV 16型（HPV 16）E6与NFX 1的两种剪接变体相互作用，以增加hTERT表达。NFX 1 -91是hTERT的转录抑制因子，其被多泛素化并且与E6相关蛋白一起被HPV 16 E6靶向降解。我们先前表明NFX 1 -123通过与细胞质多聚腺苷酸结合蛋白（PABPC）结合来增强hTERT表达。在这项研究中，我们确定，与NFX 1 -91不同，NFX 1 -123是一种细胞质蛋白，与PABPC共定位，但不与PABPC在细胞核和细胞质之间穿梭。NFX 1 -123需要其结合PABPC的PAM 2基序和具有推定的核酸结合能力的R3 H结构域，以增加表达HPV 16 E6的角质形成细胞中的hTERT mRNA水平和端粒酶活性。在表达HPV 16 E6和过表达NFX 1 -123的角质形成细胞中，与hTERT的5'非翻译区（5' UTR）融合的体外转录RNA的蛋白表达增加。这种转录后表达的增加需要PAM 2基序和NFX 1 -123的R3 H结构域以及HPV 16 E6的共表达。NFX 1 -123结合内源性hTERT mRNA并增加其在表达HPV 16 E6的人包皮角质形成细胞中的稳定性，并且NFX 1 -123增加与hTERT的5' UTR融合的体外转录的RNA的稳定性。总之，这些研究描述了在HPV 16 E6表达的角质形成细胞中通过细胞质蛋白NFX 1 -123与hTERT mRNA的直接相互作用对hTERT进行转录后调节的第一个证据。
High-risk human papillomavirus (HPV) E6 protein induces telomerase activity through transcriptional activation of hTERT, the catalytic subunit of telomerase. HPV type 16 (HPV16) E6 interacts with two splice variants of NFX1 to increase hTERT expression. NFX1-91 is a transcriptional repressor of hTERT that is polyubiquitinated and targeted for degradation by HPV16 E6 in concert with E6-associated protein. We previously showed that NFX1-123 augments hTERT expression through binding to cytoplasmic poly(A) binding proteins (PABPCs). In this study, we determined that unlike NFX1-91, NFX1-123 is a cytoplasmic protein that colocalized with PABPCs but does not shuttle with PABPCs between the nucleus and cytoplasm. NFX1-123 requires both its PAM2 motif, with which it binds PABPCs, and its R3H domain, which has putative nucleic acid binding capabilities, to increase hTERT mRNA levels and telomerase activity in keratinocytes expressing HPV16 E6. In keratinocytes expressing HPV16 E6 and overexpressing NFX1-123, there was increased protein expression from in vitro-transcribed RNA fused with the 5' untranslated region (5' UTR) of hTERT. This posttranscriptional increase in expression required the PAM2 motif and R3H domain of NFX1-123 as well as the coexpression of HPV16 E6. NFX1-123 bound endogenous hTERT mRNA and increased its stability in HPV16 E6-expressing human foreskin keratinocytes, and NFX1-123 increased the stability of in vitro-transcribed RNA fused with the 5' UTR of hTERT. Together, these studies describe the first evidence of posttranscriptional regulation of hTERT, through the direct interaction of the cytoplasmic protein NFX1-123 with hTERT mRNA, in HPV16 E6-expressing keratinocytes.