Mutations that reduce SUMO modification increase p300-mediated transcriptional activity and expression of a SUMO-specific protease or catalytically inactive Ubc9 relieved repression, demonstrating that p300 repression was mediated by SUMO conjugation.
Here, we locate the CRD1 transcriptional repression domain between residues 1017 and 1029 of p300.
Taken together, our results indicate that MN1 is a transcription coactivator rather than a sequence-specific transcription factor, and that it may stimulate RAR/RXR-mediated transcription through interaction with p160 and p300.
Cotransfection of MN1 with RAC3 or p300, known coactivators of retinoic acid receptors, leads to a further synergistic induction of transcription.
Importantly, binding of TR3 inhibits the HAT activity of p300, as the p300-induced histone H3 acetylation and transcription were repressed by the presence of TR3.
However, cotransfection of TR3 abrogated the effect of Gal4-p300/HAT in a dose-dependent manner (C), suggesting that p300-mediated gene transcription is regulated by TR3.
Since p300HAT activity is thought to stimulate transcription by acetylating Histones (,), we next examined whether the repression of p300 acetyltransferase activity by TR3 will result in inhibition of p300-activated gene transcription.
They all repress p300HAT-dependent chromatin transcription, but not transcription from DNA template.
As shown in C, Gal4-p300/HAT obviously activated the transcription of the reporter gene.
We found that CBP enhanced CLOCK/BMAL1-mediated transcription when pCAF was overexpressed in NIH3T3 cells, whereas it normally represses the activity of CLOCK/BMAL1.
Conversely, CBP repressed CLOCK/BMAL1-mediated transcription when HDAC3 was overexpressed in COS-1 cells, in which it normally enhances the activity of CLOCK/BMAL1.
As shown previously, CBP/p300 stimulates CLOCK/BMAL1-mediated transcription in COS-1 cells.
Surprisingly, although CBP enhanced CLOCK/BMAL1-mediated transcription in COS-1 cells, overexpression and RNAi-mediated knockdown experiments indicated that CBP and p300 repressed CLOCK/BMAL1-mediated transcription in NIH3T3 cells.
Consistent with this, we observed that CBP enhances CLOCK/BMAL1-mediated transcription in COS-1 cells (Figure ).
These results are in agreement with previous ones, indicating that NF-Y is required to establish a promoter architecture that facilitate transcription , the pattern of p300 binding closely matches that of NF-Y binding and promoter activation , and that p300 physically interacts with NF-Y , .
Interestingly, activation of p300-mediated transcription by MEKK1 does not appear to require the downstream kinase JNK and may involve either a direct phosphorylation of p300 by MEKK1 or by other non-JNK MEKK1-directed downstream kinases.
p300 and CREB-binding protein (CBP) are related transcriptional coactivators that possess histone acetyltransferase activity.
We identify several domains within p300 that can respond to MEKK1-induced transcriptional activation.
In the absence of ligand-activated ER, p300 was found to have little effect (less than twofold increase) on transcription, whereas, in contrast, p300 was observed to act synergistically with ligand-activated ER to enhance transcription.
In the first stroke, ER and p300 function cooperatively to increase the efficiency of productive transcription initiation.
When transcription was limited to a single round, p300 and ER were found to enhance the efficiency of transcription initiation in a cooperative manner.
Therefore, to determine which processes are transcriptionally regulated by Gcn5, we performed comparative transcriptional profiling between the wild type and the gcn5Δ mutant strain.
These large histone acetyltransferase complexes are recruited to specific gene promoters to modify local chromatin structure and thus regulate transcription.
In S. cerevisiae, Gcn5 is involved in regulating transcriptional responses to common environmental stresses, such as high temperature, oxidative damage, high osmolarity, and nutrient deprivation.
Given these prior results, we hypothesized that chromatin remodeling and transcriptional regulation via Gcn5-mediated histone acetyltransferase activity would be an important way for C. neoformans to rapidly adapt to host conditions.
In the budding yeast Saccharomyces cerevisiae, the Spt3-Ada2-Gcn5 (SAGA) complex is involved in global transcriptional regulation.
Once recruited to target promoters, p300/CBP activate transcription by acetylating histone tails or target lysines within other transcription factors using their intrinsic acetyltransferase activity.
In this report, we used the transcriptional squelching ability of E1A 12S protein to identify p300/CBP as a co-factor involved in transcriptional regulation by the E1A 13S protein.
Taken together, these results indicate for the first time that p300/CBP are critical factors for CR3-dependent transcriptional activation.
We also show that p300/CBP and their associated acetyltransferase activities are important factors for transcriptional activation by CR3.
Indeed, recent work has shown that expression of E1A 12S induces global changes in histone H3 K18 acetylation, consistent with the sequestration/retargeting of p300/CBP by E1A (). p300 and CBP are highly related transcriptional co-activators that are recruited to gene promoters via their association with numerous otherwise unrelated DNA-binding transcription factors ().
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