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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

LAP, a transcriptional activator, and LIP, a transcriptional repressor, are translated from a single mRNA species by using two AUGs within the same reading frame. These two proteins share the 145 C-terminal amino acids that contain the basic DNA-binding domain and the leucine zipper dimerization helix. Probably owing to its higher affinity for its DNA cognate sequences, LIP can attenuate the transcriptional stimulation by LAP in substoichiometric amounts. As revealed by transient transfection experiments, a moderate increase in the LAP/LIP ratio results in a significantly higher transcriptional activation of an appropriate target gene. The LAP/LIP ratio increases about 5-fold during terminal rat liver differentiation and is thus likely to modulate the activity of LAP in the intact animal.
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PMID:A liver-enriched transcriptional activator protein, LAP, and a transcriptional inhibitory protein, LIP, are translated from the same mRNA. 193 61

LAP (NF-IL6 or C/EBP beta), is a liver transcriptional activator protein that confers liver-specific gene expression. Because LAP has a characteristic phosphoacceptor sequence for cAMP-dependent protein kinase A (PKA), we tested if in vitro phosphorylation of LAP by PKA modulates its interaction with specific DNA sequences. The major PKA phosphorylation site of LAP was identified as Ser105, which is a predicted PKA site. As expected, this PKA phosphorylation site disappears after mutation of Ser105 to Ala. Kinetic studies with LAP and LAP Asp105 (which mimics a phosphoserine residue) demonstrated that phosphorylation of Ser105 itself has no effect on DNA binding. Phosphorylation of other sites by PKA, identified in the region between Ser173 and Ser223 and at Ser240, by analysis of truncated and mutated LAP peptides, resulted in an inhibition of DNA binding. LAP was also phosphorylated by purified protein kinase C in vitro, and the major phosphoacceptor was shown to be Ser240 within the DNA-binding domain of LAP. Phosphorylation of LAP at this residue or introduction of a Ser240 to Asp mutation resulted in marked decrease in its binding to DNA. These results suggest that site-specific phosphorylations of LAP modulate transactivation of its target genes.
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PMID:Protein kinase A and C site-specific phosphorylations of LAP (NF-IL6) modulate its binding affinity to DNA recognition elements. 820 Sep 92

A short non-coding region (SNR) commonly exists between the E5 and L2 open reading frames of human papillomaviruses (HPVs). Except for the poly(A) signal for early gene transcripts, no biological functions have been discovered for the SNR. To test a possible promoter-like activity of the SNR, we carried out CAT reporter assays using constructs containing the SNRs from HPV-16, -18 and -33 linked to a promoterless CAT gene. We reproducibly observed enhanced expression of CAT gene by the SNRs. Co-expression of a transcriptional activator (LAP/NF-IL6) or deletion of the poly(A) signal augmented the promoter-like activity of the SNRs. RNase protection assays revealed a LAP-inducible CAT mRNA properly initiated from the HPV-16 SNR. These results may suggest that the SNR has a promoter activity that is regulated by keratinocyte differentiation.
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PMID:Evidence for a promoter-like activity in the short non-coding region of human papillomaviruses. 860 81

The CCAAT/enhancer-binding proteins (C/EBPs) are a family of leucine-zipper transcription factors that regulate gene expression to control cellular proliferation, differentiation, inflammation and metabolism. Encoded by an intronless gene, C/EBPbeta is expressed as several distinct protein isoforms (LAP1, LAP2, LIP) whose expression is regulated by the differential use of several in-frame translation start sites. LAP1 and LAP2 are transcriptional activators and are associated with differentiation, whereas LIP is frequently elevated in proliferative tissue and acts as a dominant-negative inhibitor of transcription. However, emerging evidence suggests that LIP can serve as a transcriptional activator in some cellular contexts, and that LAP1 and LAP2 might also have unique actions. The LIP:LAP ratio is crucial for the maintenance of normal growth and development, and increases in this ratio lead to aggressive forms of breast cancer. This review discusses the regulation of C/EBPbeta activity by post-translational modification, the individual actions of LAP1, LAP2 and LIP, and the functions and downstream targets that are unique to each isoform. The role of the C/EBPbeta isoforms in breast cancer is discussed and emphasis is placed on their interactions with receptor tyrosine kinases.
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PMID:CCAAT/enhancer-binding protein beta: its role in breast cancer and associations with receptor tyrosine kinases. 1935 37