Adenovirus E1A N-Terminal Amino Acid Sequence Requirements for Repression of Transcription In Vitro and In Vivo Correlate with Those Required for E1A Interference with TBP-TATA Complex Formation

The transcription-repression domain of the adenovirus E1A oncoprotein targets p300 at the promoter

“…Transcription repression by E1A 243R in vivo is promoter-specific and targets the basal transcription machinery Several lines of evidence show that E1A repression targets the TBP component of the basal transcription machinery (Song et al, 1995a(Song et al, , 1997Boyd et al, 2002): (i) TFIID or recombinant TBP reverses transcription repression by E1A in vitro; (ii) TBP restores the ability of an E1A 1-80 affinity-depleted nuclear extract to support transcription and (iii) TBP-TATA interaction in vitro is disrupted by E1A 243R or E1A 1-80. If E1A targets the basal transcription machinery, why aren't all E1A transcription repression targets promoter-bound p300 M Green et al promoters repressed by E1A?…”

“…E1A transcription repression targets promoter-bound p300 M Green et al between sequences required for binding p300 and those essential for E1A transcription repression (Boyd et al, 2002;Loewenstein et al, 2006) and for cell transformation (Rasti et al, 2005). These observations, coupled with studies that implicate the basal transcription machinery (the TBP component of TFIID) as a functional target of E1A repression (Song et al, 1995a(Song et al, , 1997Boyd et al, 2002), suggest a two-step model of E1A repression: (i) E1A accesses a specific promoter by interaction with a DNA-bound transcription co-activator (such as p300) and (ii) E1A disrupts TBP-TATA interaction at that promoter (Figure 1).…”

“…A recombinant protein containing only the N-terminal 80 amino acids strongly represses transcription of E1A-repressible promoters in a manner that recapitulates the repression activity of the full-length E1A 243R protein in vitro and in vivo (Song et al, 1995a(Song et al, -c, 1997Boyd et al, 2002;Loewenstein et al, 2006). A detailed mutational/functional analysis has identified two regions or sub-domains that are critical for E1A repression: amino acids approximately 1-30 and approximately 48-60.…”

“…Key amino acids in the first sub-domain include (i) residues 2-6 with 6Cys being especially important, and (ii) residue 20Leu. All of these residues are essential for the transcription-repression function and for disruption of a TBP-TATA complex, but only amino-acid residue 6 appears to be critical for binding p300 under in vitro conditions (Boyd et al, 2002). Of interest, the E1A N-terminus can interact with the DNA methyltransferase, Dnmt1, and this reaction is abolished by a point mutation at Leu 20 of E1A (Burgers et al, 2007), which is critical for E1A transcription repression (Boyd et al, 2002).…”

“…All of these residues are essential for the transcription-repression function and for disruption of a TBP-TATA complex, but only amino-acid residue 6 appears to be critical for binding p300 under in vitro conditions (Boyd et al, 2002). Of interest, the E1A N-terminus can interact with the DNA methyltransferase, Dnmt1, and this reaction is abolished by a point mutation at Leu 20 of E1A (Burgers et al, 2007), which is critical for E1A transcription repression (Boyd et al, 2002). In contrast, amino acids 53Ala, 54Pro, 55Glu and 56Asp within the second sub-domain are important for the E1A repression function and for binding of E1A's cellular partner p300, but not for binding TBP or for disruption of a TBP-TATA complex (Loewenstein et al, 2006).…”