Functional redundancy of octamer elements in the mouse mammary tumor virus promoter

Huang, Mike; Lee, Jae Woon; Peterson, D O

doi:10.1093/nar/21.22.5235

Cited by 11 publications

(10 citation statements)

References 53 publications

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“…Alternatively, the two regulatory sites may act at different stages of development, since Cdc14 transcripts persist from early sporulation until cyst germination (1). Genes regulated by multiple inputs via distinct promoter modules are common in prokaryotes and eukaryotes, as are promoters containing functionally redundant transcription factor sites (16,18,25).…”

Section: Discussionmentioning

confidence: 99%

Architecture of the Sporulation-Specific Cdc14 Promoter from the Oomycete Phytophthora infestans

2007

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The Cdc14 gene of Phytophthora infestans is transcribed specifically during sporulation, with no mRNA detectable in vegetative hyphae, and is required for sporangium development. To unravel the mechanisms regulating its transcription, mutated Cdc14 promoters plus chimeras of selected Cdc14 sequences and a minimal promoter were tested in stable transformants. This revealed that a tandem repeat of three copies of the motif CTYAAC, located between 67 and 90 nucleotides (nt) upstream of the major transcription start site, is sufficient to determine sporulation-specific expression. All three repeats need to be present for activity, suggesting that they bind a transcription factor through a cooperative mechanism. Electrophoretic mobility shift assays indicated that the CTYAAC repeats are specifically bound by a protein in nuclear extracts. Evidence was also obtained for a second region within the promoter that activates Cdc14 transcription during sporulation which does not involve those repeats. The CTYAAC motif also affects the specificity of transcription initiation. Wild-type Cdc14 is transcribed from a major start site and minor site(s) located about 100 nt upstream of the major site. However, stepwise mutations through the CTYAAC triad caused a graded shift to the upstream sites, as did mutating bases surrounding the major start site; transcripts initiated from the upstream site remained sporulation specific. Replacing the Cdc14 initiation region with the Inr-like region of the constitutive Piexo1 gene had no apparent effect on the pattern of transcription. Therefore, this study reports the first motif determining sporulation-induced transcription in oomycetes and helps define oomycete core promoters.

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Section: Discussionmentioning

confidence: 99%

Architecture of the Sporulation-Specific Cdc14 Promoter from the Oomycete Phytophthora infestans

2007

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“…Ample evidence suggests that the MMTV LTR is occupied by an array of six nucleosomes (16,70) that have compositions typical of eukaryotic chromatin (two each of histones H2A, H2B, H3, and H4) (72). Chromatin structure has been shown to change in the presence of glucocorticoids (69,70,86,98), and it is believed that this change allows promoter activation through the binding of transcriptional activators such as NF-1 and Oct-1 and the basal transcription apparatus (20,48). In agreement with this idea is the recent observation that the RNA polymerase II holoenzyme contains SWI/SNF, a protein complex that can disrupt nucleosomes (94).…”

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confidence: 99%

The Matrix Attachment Region-Binding Protein SATB1 Participates in Negative Regulation of Tissue-Specific Gene Expression

Liu

Bramblett

Zhu

et al. 1997

Molecular and Cellular Biology

113

150

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The nuclear matrix has been implicated in several cellular processes, including DNA replication, transcription, and RNA processing. In particular, transcriptional regulation is believed to be accomplished by binding of chromatin loops to the nuclear matrix and by the concentration of specific transcription factors near these matrix attachment regions (MARs). A number of MAR-binding proteins have been identified, but few have been directly linked to tissue-specific transcription. Recently, we have identified two cellular protein complexes (NBP and UBP) that bind to a region of the mouse mammary tumor virus (MMTV) long terminal repeat (LTR) previously shown to contain at least two negative regulatory elements (NREs) termed the promoter-proximal and promoter-distal NREs. These NREs are absent from MMTV strains that cause T-cell lymphomas instead of mammary carcinomas. We show here that NBP binds to a 22-bp sequence containing an imperfect inverted repeat in the promoter-proximal NRE. Previous data showed that a mutation (p924) within the inverted repeat elevated basal transcription from the MMTV promoter and destabilized the binding of NBP, but not UBP, to the proximal NRE. By using conventional and affinity methods to purify NBP from rat thymic nuclear extracts, we obtained a single major protein of 115 kDa that was identified by protease digestion and partial sequencing analysis as the nuclear matrix-binding protein special AT-rich sequence-binding protein 1 (SATB1). Antibody ablation, distamycin inhibition of binding, renaturation and competition experiments, and tissue distribution data all confirmed that the NBP complex contained SATB1. Similar types of experiments were used to show that the UBP complex contained the homeodomain protein Cux/CDP that binds the MAR of the intronic heavy-chain immunoglobulin enhancer. By using the p924 mutation within the MMTV LTR upstream of the chloramphenicol acetyltransferase gene, we generated two strains of transgenic mice that had a dramatic elevation of reporter gene expression in lymphoid tissues compared with reporter gene expression in mice expressing wild-type LTR constructs. Thus, the 924 mutation in the SATB1-binding site dramatically elevated MMTV transcription in lymphoid tissues. These results and the ability of the proximal NRE in the MMTV LTR to bind to the nuclear matrix clearly demonstrate the role of MAR-binding proteins in tissue-specific gene regulation and in MMTV-induced oncogenesis.The nuclear matrix is a network of RNA and nonhistone proteins that serves as a scaffold for loops of chromatin (10,11,64). This matrix has been associated with the regulation of DNA replication, transcription, and RNA processing (for a review, see reference 64). The DNA regions anchoring chromatin to the matrix (called matrix-associated regions [MARs] or scaffold-associated regions) (18) are composed of AT-rich sequences that have a unique structure characterized by high unwinding potential and the formation of a narrow minor groove (1, 52). MARs have been shown to colocal...

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“…The MMTV promoter contains three overlapping octamer-related sequences between the TATA box and a binding site for NF-1. We (26,58), as well as others (5), have reported specific binding to these sequences by proteins present in nuclear extracts of various cultured cell lines, and our results strongly suggested that only the nonoverlapping octamer-related elements most proximal and most distal to the transcription start site are efficiently recognized (26). In addition, Brüggemeier et al (5) have reported that partially purified Oct-1 binds to the MMTV octamer-related sequences; however, the Oct-1 preparation used in these studies was not extensively described.…”

Section: Discussionmentioning

confidence: 99%

“…We have previously demonstrated that octamer-related sequences are important for both basal and steroid hormone-induced MMTV promoter activity in a transient-transfection assay in mouse Ltk Ϫ cells (26,58). To begin to determine the molecular details of the role of octamer-related sequences in MMTV promoter activity, we turned to in vitro transcription assays.…”

Section: Mutations In Octamer-related Sequences Decrease Mmtv Promotementioning

confidence: 99%

“…We used gel electrophoresis mobility shift assays to demonstrate that the most distal (dOct) and most proximal (pOct) of the three overlapping octamer-related elements are recognized by a common protein present in nuclear extracts of cultured cells, while the central element (cOct) is not efficiently recognized (26). Furthermore, the dOct and pOct elements appear to be, at least to some extent, functionally redundant, in that linkerscanning (LS) mutations in a single element have relatively little effect on promoter activity compared to alteration of the entire MMTV octamer region (58), and deletion of one Oct element has little effect on transcription as long as certain spacing constraints among remaining promoter elements are maintained (26). However, the protein(s) that mediates the effect of octamer-related elements on basal levels of MMTV transcription has not been clearly identified.…”

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Stimulation of basal transcription from the mouse mammary tumor virus promoter by Oct proteins

Kim

Peterson

1995

J Virol

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The steroid hormone-inducible promoter of mouse mammary tumor virus (MMTV) contains three overlapping sequences related to the consensus octamer motif ATGCAAAT. Basal promoter activity in the absence of hormone induction from a template in which all three octamer elements were mutated was decreased by twoto threefold in in vitro transcription assays. Oct-1 protein purified from HeLa cell nuclear extracts, as well as recombinant Oct-1 expressed in bacteria, recognized MMTV octamer-related sequences, as shown by DNase I footprinting. Furthermore, rabbit polyclonal antiserum directed against recombinant Oct-1 completely inhibited the formation of specific complexes between MMTV octamer-related sequences and proteins present in nuclear extracts of HeLa cells, indicating that Oct-1 is the major protein in HeLa nuclear extracts that recognizes octamer-related sequences in the MMTV promoter. In addition, depletion of Oct-1 from the nuclear extract by using Oct-1-specific antiserum or a sequence-specific DNA affinity resin decreased in vitro transcription from the wild-type MMTV promoter to a level identical to that obtained from a promoter in which all three octamer-related sequences were mutated. Addition of purified HeLa Oct-1 or recombinant Oct-1 to the depleted extract selectively increased transcription from the wild-type relative to the mutated promoter, demonstrating that Oct-1 transcription factor stimulates basal transcription from the MMTV promoter. A similar effect was observed when purified recombinant Oct-2 was added to the Oct-1-depleted extract, suggesting that Oct-2 may play an important role in MMTV transcription in B cells.

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Functional redundancy of octamer elements in the mouse mammary tumor virus promoter

Cited by 11 publications

References 53 publications

Architecture of the Sporulation-Specific Cdc14 Promoter from the Oomycete Phytophthora infestans

Architecture of the Sporulation-Specific Cdc14 Promoter from the Oomycete Phytophthora infestans

The Matrix Attachment Region-Binding Protein SATB1 Participates in Negative Regulation of Tissue-Specific Gene Expression

Stimulation of basal transcription from the mouse mammary tumor virus promoter by Oct proteins

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