1,721,052 research outputs found
Overexpression of ubiquitin downregulates transcription of the endogenous UbC gene in HeLa cells
No full text32nd FEBS Congressw, MOLECULAR MACHINE
Ubiquitin over-expression promotes E6AP degradation and reactivation of the p53/mdm-2 pathway
No full text32nd FEBS Congress, Molecular Machine
De-ubiquitylation is the most critical step in the ubiquitin mediated homeostatic control of the NF-kB/IKK basal activity
No full textThe role of ubiquitylation in signal-induced
activation of nuclear factor -kB (NF-kB) has been well
established, while its involvement in maintaining NF-kB
basal activity is less certain. Recent evidences demonstrate
that in unstimulated cells, NF-kB homeostasis is actually
the result of opposing forces: pro-activating activity of the
IkB Kinase (IKK) and inhibitory activity of the Inhibitor of
-kB (IkB) proteins. It is well known that endogenous deubiquitylating
mechanisms are less effective on Ub motifs
containing UbG76A. Here, we show that overexpression of
a ubiquitin (Ub) G76A mutant leads to persistent activation
of the IKK/NF-kB pathway in the absence of extra-cellular
stimuli. In contrast, no effects on NF-kB activation were
observed upon expression of UbK48R and UbK63R
mutants, which are known to impair elongation of Lys48-
and Lys63-linked poly-ubiquitin chains, respectively.
Overall, these findings indicate that under basal conditions,
the rate of de-ubiquitylation, rather than that of substrate
ubiquitylation, is critical for the maintenance of appropriate
levels of IKK/NF-kB activity
A potent enhancer element in the 5'-UTR intron is crucial for transcriptionalregulation of the human ubiquitin C gene
No full textUbiquitin (Ub) plays a crucial role in almost every aspect of cellular functions. It is encoded by four genes, of
which UbC is known to meet cell demand for ubiquitin in both basal and stressful conditions. To understand
the molecular mechanisms regulating UbC gene expression, we performed a functional characterization of
the UbC promoter. Deletion analyses on the 5′ end of the −916/+878 promoter region, excluded the
functional importance of nt −916/−371 in the transcriptional regulation of the gene, while 3′ deletions
revealed that intron removal (nt+65/+876) resulted in a marked reduction of promoter activity in all the
reporter constructs, regardless of the cell types. Intron substitution with a heterologous chimeric intron
failed to restore promoter activity, thus allowing to exclude that the splicing event, per se, can be responsible
for the intron-mediated burst of transcription. Gel shift assays demonstrated nuclear factor binding with the
+137/+766 intron region. Reporter constructs carrying partial intron deletions confirmed that this
sequence is, indeed, required for maximal transcriptional activity. Computer-based analysis found potential
Sp1 binding motifs within the intron sequence and electrophoretic mobility shift and supershift assays
demonstrated that both Sp1 and Sp3 transcription factors interact, in vitro, with the UbC intron, at multiple
binding sites. Moreover, ectopic expression of Sp1 and Sp3 revealed that both transcription factors positively
regulate UbC promoter activity. Collectively, our data highlight the very new evidence that the 5′-UTR intron
is crucial in regulating UbC gene expression and provide insights into the pivotal role of Sp1/Sp3 binding to
the intronic enhancer in the regulation of UbC transcription
Drug-loaded red blood cells for the control of the inflammatory response: selective targeting of nuclear factor-kB (NF-kB)
No full textUp-regulation of the ubiquitin-conjugating and proteolytic systems in murine acquired immunodeficiency syndrome
No full text
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