Binding of SNAPc, Oct-1, and Staf to Type 3 Promoter

Stable Identifier
Reaction [binding]
Homo sapiens
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SNAPc binds specifically to the PSE. This binding is mediated in part by an unusual Myb domain within SNAP190 (Mittal et al., 1999; Wong et al., 1998). However, even though a SNAP190 segment consisting of just the Myb domain binds DNA, within the complex the Myb domain is not sufficient for binding. The smallest characterized subassembly of SNAPc subunits that binds specifically to DNA consists of SNAP190 aa 84-505, SNAP43 aa 1-268, and SNAP50 (Ma and Hernandez, 2000). Consistent with the requirement for parts of SNAP190 and SNAP50 for DNA binding, UV cross-linking experiments suggest that both SNAP190 (Yoon et al., 1995) and SNAP50 (Henry et al., 1996) are in close contact with DNA.

The binding of SNAPc to the PSE is stabilized by a number of cooperative interactions with other members of the transcription initiation complex including Oct-1, TBP, and Brf2.

The binding of SNAPc to the core promoter is stabilized by a direct protein-protein contact with the Oct-1 POU domain.

SNAPc does not bind very efficiently to the PSE on its own. It contains a damper of DNA binding that resides within the C-terminal two thirds of SNAP190 and/or SNAP45, because a subcomplex of SNAPc (mini-SNAPc) lacking these sequences binds much more efficiently to DNA than complete SNAPc (Mittal et al., 1999). The damper within SNAPc is deactivated, probably through a conformational change, by a direct protein-protein contact with the Oct-1 POU domain. The transcription initiation complex is illustrated in Figure 6. The protein-protein contact between the Oct-1 POU domain and SNAPc involves a glutamic acid at position 7 within the Oct-1 POUS domain and a lysine at position 900 within SNAP190, which are symbolized in Figure 6 by small triangles (Ford et al., 1998; Hovde et al., 2002; Mittal et al., 1999). The octamer sequence within the DSE and the PSE are separated by more than 150 base pairs, but the direct protein-protein contact is rendered possible by the presence of a positioned nucleosome between the DSE and the PSE, which, as shown in the figure, probably brings into close proximity the Oct-1 POU domain and SNAPc (Stunkel et al., 1997; Zhao et al., 2001).

Literature References
PubMed ID Title Journal Year
11463379 A positioned nucleosome on the human U6 promoter allows recruitment of SNAPc by the Oct-1 POU domain

Hernandez, N, Pendergrast, PS, Zhao, X

Mol. Cell 2001
9234698 A nucleosome positioned in the distal promoter region activates transcription of the human U6 gene

Kober, I, St√ľnkel, W, Seifart, KH

Mol. Cell. Biol. 1997
9418884 The large subunit of basal transcription factor SNAPc is a Myb domain protein that interacts with Oct-1

Matthias, P, Ma, B, Hernandez, N, Klages, N, Strubin, M, Kobayashi, R, Henry, RW, Wong, MW

Mol. Cell. Biol. 1998
11056176 A map of protein-protein contacts within the small nuclear RNA-activating protein complex SNAPc

Ma, B, Hernandez, N

J. Biol. Chem. 2001
9003788 Cloning and characterization of SNAP50, a subunit of the snRNA-activating protein complex SNAPc

Ma, B, Hernandez, N, Sadowski, CL, Kobayashi, R, Henry, RW

EMBO J. 1996
10421633 SNAP(c): a core promoter factor with a built-in DNA-binding damper that is deactivated by the Oct-1 POU domain

Mittal, V, Ma, B, Hernandez, N

Genes Dev. 1999
7891697 Proximal sequence element-binding transcription factor (PTF) is a multisubunit complex required for transcription of both RNA polymerase II- and RNA polymerase III-dependent small nuclear RNA genes

Yoon, JB, Wang, Z, Murphy, S, Bai, L, Roeder, RG

Mol. Cell. Biol. 1995
Orthologous Events
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