Cis-Acting Negative RNA Elements on Papillomavirus Late mRNAs

Schwartz, Stefan

doi:10.1006/smvy.1997.0131

Cited by 22 publications

(29 citation statements)

References 44 publications

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“…RNA instability elements in the L1 and L2 ORFs may function to reduce the late mRNA half-lives to prevent untimely production of the L1 and L2 in infected proliferating cells. The mRNAs would then be stabilized in terminally differentiated cells, and as a result, L1 and L2 proteins and virions would be produced in the superficial layers of the epithelium, as discussed in detail previously (5,24,26,31).…”

Section: Discussionmentioning

confidence: 99%

“…From an evolutionary point of view, it is also clear that HPV-16 has been optimized for replication and expression in human cells, since no other host is known for HPV-16. A more likely explanation for the low expression levels of the HPV-16 L1 and L2 genes from subgenomic expression plasmids is therefore that HPV-16 has evolved to contain distinct regulatory RNA elements that are necessary for an ordered and highly regulated late gene expression, RNA sequences that probably contributed to the successful establishment of HPV-16 in the human population (24)(25)(26). Interestingly, "codon-optimized" early papillomavirus genes also display enhanced expression levels (9,20), and it would be interesting to investigate the mechanisms behind the improved protein production from these mutants.…”

Section: Discussionmentioning

confidence: 99%

“…We are interested in the regulation of HPV late gene expression, and we and others have identified inhibitory sequences on late HPV mRNAs (1,(24)(25)(26). These sequences are located in the late 3Ј untranslated region (6,15,17,18,33) and in the L1 and L2 coding regions (4,5,28,31).…”

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confidence: 99%

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Mutational Inactivation of Two Distinct Negative RNA Elements in the Human Papillomavirus Type 16 L2 Coding Region Induces Production of High Levels of L2 in Human Cells

Öberg

Collier

Zhao

et al. 2003

J Virol

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Here we show that the 5 end and the middle region of the L2 coding sequence of human papillomavirus type 16 contain strong inhibitory RNA sequences termed inhibitory regions I and II. This is in contrast to L1, which contains one inhibitory region in the 5 end of the coding region. Inhibitory regions I and II acted in cis to reduce L2 mRNA levels and to inhibit the use of the mRNA. In tandem, the two regions reduced L2 mRNA production to undetectable levels. Specific mutational inactivation of the two inhibitory elements in the 5 end and in the middle region of L2 by the introduction of nucleotide substitutions that changed the nucleotide sequence but not the protein sequence resulted in production of high levels of L2 mRNA and protein. In contrast to L2, a partial L1 mutant in which only the first one third of L1 was mutated produced levels of L1 mRNA and protein similar to those in a full L1 mutant. In addition, the constitutive transport element of simian retrovirus type 1 overcomes the effect of the inhibitory sequences of L1 but not L2.Human papillomaviruses (HPVs) are a group of small, double-stranded DNA tumor viruses (27). The HPV genome is approximately 8 kb in length and can be divided into an early (E) and late (L) region ( Fig. 1) (16). The late region codes for the two structural proteins L1 and L2, which are the major and minor capsid proteins, respectively. Together they form the icosahedral capsid that contains the viral genomic DNA.The HPV life cycle is tightly linked to the differentiation stage of the infected cell (16). Upon entry into the basal epithelial cells, only early genes are expressed. As the cell progresses towards terminal differentiation, induction of viral DNA replication occurs to high levels (30). This is followed by activation of viral late gene expression and assembly of infectious viral particles at the uppermost layers of the epithelium. The requirement for terminal cell differentiation has hampered the study of the viral life cycle in vitro. However, propagation of papillomavirus has been successful in a xenograft model and in the organotypic (raft) culture systems that induce terminal cell differentiation (10,21,29). Propagation of HPVcontaining cell lines in these systems leads to the completion of the differentiation-dependent life cycle of HPVs in vitro. The L1 and L2 proteins were detected only after culturing of the HPV DNA-containing cells in raft cultures and then only in the superficial layers of the terminally differentiated cells (12-14, 21-23). L1 and L2 proteins were not seen in the proliferating keratinocytes, demonstrating that expression of L1 and L2 is efficiently suppressed in proliferating cells.We are interested in the regulation of HPV late gene expression, and we and others have identified inhibitory sequences on late HPV mRNAs (1, 24-26). These sequences are located in the late 3Ј untranslated region (6,15,17,18,33) and in the L1 and L2 coding regions (4,5,28,31). Our previous work on HPV-16 L1 expression demonstrated the presence of cis-acting negat...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Mutational Inactivation of Two Distinct Negative RNA Elements in the Human Papillomavirus Type 16 L2 Coding Region Induces Production of High Levels of L2 in Human Cells

Öberg

Collier

Zhao

et al. 2003

J Virol

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“…Since L2 and L1 can be detected only in terminally differentiated epithelial cells infected with HPV, we proposed that these RNA elements regulate late gene expression in a differentiation-dependent manner in the viral life cycle (32)(33)(34). Early in infection, factors would bind to the elements and destabilize the RNA.…”

Section: Discussionmentioning

confidence: 99%

“…This mutant L2 gene produced high levels of L2 mRNA and L2 protein, indicating that inhibitory RNA elements in L2 had been inactivated (30). We speculated that the role of these elements in the viral life cycle was to regulate HPV-16 polyadenylation and/or splicing (30,(32)(33)(34). We previously identified inhibitory elements in the 5Ј end of the HPV-16 L1 coding region (10,40) and later showed that they are exonic splicing silencers that inhibit HPV-16 late mRNA splicing (49).…”

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A Downstream Polyadenylation Element in Human Papillomavirus Type 16 L2 Encodes Multiple GGG Motifs and Interacts with hnRNP H

Öberg

Fay²,

Lambkin³

et al. 2005

J Virol

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Production of human papillomavirus type 16 (HPV-16) virus particles is totally dependent on the differentiation-dependent induction of viral L1 and L2 late gene expression. The early polyadenylation signal in HPV-16 plays a major role in the switch from the early to the late, productive stage of the viral life cycle. Here, we show that the L2 coding region of HPV-16 contains RNA elements that are necessary for polyadenylation at the early polyadenylation signal. Consecutive mutations in six GGG motifs located 174 nucleotides downstream of the polyadenylation signal resulted in a gradual decrease in polyadenylation at the early polyadenylation signal. This caused read-through into the late region, followed by production of the late mRNAs encoding L1 and L2. Binding of hnRNP H to the various triple-G mutants correlated with functional activity of the HPV-16 early polyadenylation signal. In addition, the polyadenylation factor CStF-64 was also found to interact specifically with the region in L2 located 174 nucleotides downstream of the early polyadenylation signal. Staining of cervix epithelium with anti-hnRNP H-specific antiserum revealed high expression levels of hnRNP H in the lower layers of cervical epithelium and a loss of hnRNP H production in the superficial layers, supporting a model in which a differentiation-dependent down regulation of hnRNP H causes a decrease in HPV-16 early polyadenylation and an induction of late gene expression.The human papillomaviruses (HPVs) are small DNA tumor viruses (20). To date, more than 100 different types have been identified (12). Some of these HPV types, termed high-risk types, are associated with development of cancer of the uterine cervix, one of the most common cancers in women worldwide (35,50). HPV type 16 (HPV-16) is the most common high-risk type (51). The HPV genome can be divided into an early region and a late region, followed by the proximal early (pAE) and the distal late (pAL) polyadenylation signals, respectively (Fig. 1A) (4). A polyadenylation signal consists of an AA UAAA sequence located 10 to 30 nucleotides (nt) upstream of the cleavage site and a degenerate GU-rich sequence element about 30 nucleotides downstream of the cleavage site (45). Some polyadenylation signals are followed by G-rich downstream elements (2, 3). The weak binding of cleavage/polyadenylation specificity factor (CPSF) to the AAUAAA motif is enhanced by CStF binding to the downstream GU-rich element (45). Recently, it was shown that U-rich upstream polyadenylation elements interact with hFip-1, an integral part of CPSF (21). In the early stage of the viral life cycle, all viral transcripts are polyadenylated at the pAE, whereas both the pAE and the pAL are used in the late, productive stage of the infection (26). In response to differentiation of the HPV-infected cell, the use of the pAE is down regulated, resulting in read-through into the late region and polyadenylation of the late transcripts at the pAL. Efficient polyadenylation at the pAE is an absolute requirement for early...

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Inhibitory activity of the human papillomavirus type 1 AU-rich element correlates inversely with the levels of the elav-like HuR protein in the cell cytoplasm

Carlsson

Schwartz

2000

Archives of Virology

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We have analysed the activity of the negative element in the late 3' untranslated region of the cutaneous human papillomavirus type 1 (HPV-1) mRNAs in a panel of epithelial cells, of both mucosal and cutaneous origin. The inhibitory activity was cell line dependent. Determination of the levels of heterogeneous ribonucleoprotein C1/C2 and HuR that have been shown previously to interact specifically with the HPV-1 negative RNA element revealed that low levels of the HuR protein in the cytoplasmic fraction correlated with high inhibitory activity of the HPV-1 element, whereas cell lines displaying low inhibitory activity contained high levels of HuR in the cytoplasm. These results suggested that the HuR protein has a positive effect on HPV-1 late gene expression.

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Cis-Acting Negative RNA Elements on Papillomavirus Late mRNAs

Cited by 22 publications

References 44 publications

Mutational Inactivation of Two Distinct Negative RNA Elements in the Human Papillomavirus Type 16 L2 Coding Region Induces Production of High Levels of L2 in Human Cells

Mutational Inactivation of Two Distinct Negative RNA Elements in the Human Papillomavirus Type 16 L2 Coding Region Induces Production of High Levels of L2 in Human Cells

A Downstream Polyadenylation Element in Human Papillomavirus Type 16 L2 Encodes Multiple GGG Motifs and Interacts with hnRNP H

Inhibitory activity of the human papillomavirus type 1 AU-rich element correlates inversely with the levels of the elav-like HuR protein in the cell cytoplasm

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