Leucine residues in conserved region of 33K protein of bovine adenovirus – 3 are important for binding to major late promoter and activation of late gene expression

ABSTRACT The human papillomavirus (HPV) life cycle is linked to the differentiation state of the host cell. In virus-infected undifferentiated basal epithelial cells, HPV genomes are maintained as episomes at low copy number. Upon differentiation, a concomitant increase in viral copy number and an induction of late gene expression from a differentiation-specific promoter is seen. To investigate whether late gene expression was dependent on the amplification of the viral genome, inhibitors of DNA replication and in vitro systems for epithelial differentiation were used in conjunction with cells that stably maintain HPV31 episomes. Treatment of cells induced to differentiate in methylcellulose with the DNA synthesis inhibitor cytosine β-arabinofuranoside (AraC) blocked viral DNA amplification but did not prevent induction of late transcription. This suggests that late gene expression does not strictly require amplification of the viral genome and that differentiation signals alone are sufficient to activate transcription from the late promoter. However, DNA amplification does appear to be necessary for maximal induction of the late promoter. In order to examine the cis-acting elements that contribute to the activation of the late promoter, a transient reporter assay was developed. In these assays, an induction of late gene expression was seen upon differentiation that was specific to the late promoter. Mapping studies localized important regulatory elements to the E6/E7 region and identified short sequences that could serve as binding sites for transcription factors. Elements within the upstream regulatory region were also found to positively and negatively influence transcription from the late promoter. These results identify mechanisms important for the differentiation-dependent activation of late gene expression of high-risk papillomaviruses.

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Extended Function of Plasmid Partition Genes: the Sop System of Linear Phage-Plasmid N15 Facilitates Late Gene Expression

Journal of Bacteriology ◽

10.1128/jb.01993-07 ◽

2008 ◽

Vol 190 (10) ◽

pp. 3538-3545 ◽

Cited By ~ 5

Author(s):

Nikolai V. Ravin ◽

Jérôme Rech ◽

David Lane

Keyword(s):

Gene Expression ◽

Late Gene ◽

Northern Hybridization ◽

Partition Functions ◽

Wild Type ◽

Late Promoter ◽

Late Gene Expression ◽

Reading Frame ◽

Partition System ◽

Plasmid Partition

ABSTRACT The mitotic stability of the linear plasmid-prophage N15 of Escherichia coli depends on a partition system closely related to that of the F plasmid SopABC. The two Sop systems are distinguished mainly by the arrangement of their centromeric SopB-binding sites, clustered in F (sopC) and dispersed in N15 (IR1 to IR4). Because two of the N15 inverted repeat (IR) sites are located close to elements presumed (by analogy with phage λ) to regulate late gene expression during the lytic growth of N15, we asked whether Sop partition functions play a role in this process. In N15, a putative Q antiterminator gene is located 6 kb upstream of the probable major late promoter and two intrinsic terminator-like sequences, in contrast to λ, where the Q gene is adjacent to the late promoter. Northern hybridization and lacZ reporter activity confirmed the identity of the N15 late promoter (p52), demonstrated antiterminator activity of the Q analogue, and located terminator sequences between p52 and the first open reading frame. Following prophage induction, N15 mutated in IR2 (downstream from gene Q) or IR3 (upstream of p52) showed a pronounced delay in lysis relative to that for wild-type N15. Expression of ir3 −-p52::lacZ during N15 wild-type lytic growth was strongly reduced relative to the equivalent ir3 + fusion. The provision of Q protein and the IR2 and SopAB proteins in trans to ir3 +-p52::lacZ increased expression beyond that seen in the absence of any one of these factors. These results indicate that the N15 Sop system has a dual role: partition and regulation of late gene transcription during lytic growth.

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Activity of simian virus 40 late promoter elements in the absence of large T antigen: evidence for repression of late gene expression.

Journal of Virology ◽

10.1128/jvi.60.2.400-404.1986 ◽

1986 ◽

Vol 60 (2) ◽

pp. 400-404 ◽

Cited By ~ 6

Author(s):

J C Alwine ◽

J Picardi

Keyword(s):

Gene Expression ◽

Simian Virus 40 ◽

Simian Virus ◽

T Antigen ◽

Late Gene ◽

Large T Antigen ◽

Late Promoter ◽

Late Gene Expression ◽

Promoter Elements

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ORF98 ofAutographa californicanucleopolyhedrosisvirusis an auxiliary factor in late gene expression

Canadian Journal of Microbiology ◽

10.1139/w03-022 ◽

2003 ◽

Vol 49 (3) ◽

pp. 157-163 ◽

Cited By ~ 5

Author(s):

Kathleen L Hefferon

Keyword(s):

Gene Expression ◽

Autographa Californica ◽

Late Gene ◽

Late Promoter ◽

Late Gene Expression ◽

Baculovirus Infection ◽

The Family ◽

Auxiliary Factor ◽

Late Expression ◽

Early Late

Autographa californica nucleopolyhedrosisvirus (AcMNPV) is the type member of the family Baculoviridae. Gene expression of AcMNPV during virus infection is temporally regulated. A series of late expression factors (LEFs) are required for late gene expression to take place. A number of additional factors have also been shown to more modestly influence late gene expression. Using the LEF transient assay, we scanned the AcMNPV genome for such factors by replacing plasmids using the LEF genes with larger clones and then looked for increases in late gene expression using a reporter plasmid under the control of a late promoter. Using this approach, ORF98 was identified as having a stimulatory effect on late gene expression. The ability of ORF98 to influence early, late, and very late gene expression was established. Furthermore, tagged versions of ORF98 were localized to the nuclei of transfected cells and were shown to interact with each other as homo-oligomers. Potential roles of ORF98 in baculovirus infection are discussed.Key words: AcMNPV, late expression factors, transactivator, gene expression.

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