Polypyrimidine tract

Figure 28-22 Assembly and action of the spliceosomal complex. Four special sequence elements control the process the 5 and 3 splice sites, the branch point (adenosine A), and a polypyrimidine tract. The snRNP particle U1 locates the 5 splice site and U2 the branch point. The tri-snRNP U4 U6 U5 then binds, U6 recognizing the 5 splice site, and U1 and U4 are released. The 2 -OH of the branch point adenosine attacks the phos-phodiester linkage to form a lariet intermediate, which releases the intron in a lariet form in the final step. After Valcarcel and Green.612...

Anwar, A., Ali, N., Tanveer, R. and Siddiqui, A. (2000) Demonstration of functional requirement of polypyrimidine tract-binding protein by SELEX RNA during hepatitis C virus internal ribosome entry site-mediated translation initiation. J. Biol. Chem., 275, 34231-34235. 

Singh, R., Valcarcel, J. and Green, M.R. (1995) Distinct binding specificities and functions of higher eukaryotic polypyrimidine tract-binding proteins. Science, 268,1173-1176. 

In a patient with congenital myasthenic syndrome, we identified that CHRNAl IVS3-8G>A attenuates binding of hnRNP /f 100-fold and causes exclusive inclusion of the downstream exon P3A (Masuda et al., 2008) (Fig. 4). We also identified that polypyrimidine tract binding protein (PTB) silences recognition of exon P3A and tannic acid facilitates the expression of PTB by activating its promoter region (Gao et al., 2009). 

For heterogeneous polypurine polypyrimidine tracts, the effect of various divalent metal ions on the transition to and stability of the H-DNA triplexes can be very different depending on the seqnence of snch For... 

Polypyrimidine tract-binding protein, a repressive regulator of protein splicing also pulmonary tuberculosis Protein transduction domain... 

Rusche, J.J., and Hurley, L.H., Facilitation of a structural transition in the polypurine/polypyrimidine tract within the proximal promoter region in the human VEGF gene by the presence of potassium and G-quadruplex-interactive agents, Nucleic Acids Res. 33, 6070-6080, 2005. 

Jamison, S.F. and Garcia, B.M. (1992). An ATP-independent U2 small nuclear ribonucleoprotein particle/precursor mRNA complex requires both splice sites and the polypyrimidine tract. Proc. Natl. Acad. Sci. USA 89, 5482-5486. 

Fig. 4.1. Mobility shift analysis Mobility shift analysis performed by 4% PAGE in 50 mM Tris-glycine 1 mM EDTA. The mobility shift is induced by the 60 kD polypyrimidine tract binding protein to a 220 nucleotide random labelled pre-mRNA transcript. The experiment shows dimeric binding (2. complex) of the protein at...

Fig. 4.5. Mg2+-dependence of the identity of UV cross-linked proteins. A randomly labelled 5 untranslated region from a growth factor mRNA was mixed with a cytoplasmic lysate at increasing Mg2+ concentrations in the binding buffer, and UV cross-linking was carried out as described in the text. PTB is the polypyrimidine tract binding protein, p50 is the major core protein of mRNPs, and p69 is a leader-specific binding protein.

A region of C/T bias upstream of the 3 splice site (polypyrimidine tract)... 

An optional region joining the polypyrimidine tract and the 3 splice site... 

The widespread occurrence of polypurine polypyrimidine tracts in eukaryotic DNA suggests that these sequences may have a biological function. Analysis of eukaryotic sequence databases reveals thousands of polypurine polypyrimidine tracts, many with the potential for triplex formation. These polypurine regions of DNA can potentially influence biology in several ways. They could provide binding sites for regulatory proteins, influ-... 

The pre-mRNA contains several defined regions to which the spliceosome will bind. Besides the 5 and 3 splice sites (5 ss and 3 ss), introns contain a branch point sequence (BPS) some 18-40 nucleotides downstream of the 3 ss, as well as a polypyrimidine tract (PPT) between BPS and 3 ss. 

Figure 22.1 Overview of the splicing process. The UI snRNP binds the 5 ss, while SFl attaches to the branch point sequence (BPS) and U2AF to polypyrimidine tract (Y ) and 3 ss to form E complex. U2 snRNP replaces SFl and U2AF, thereby creating A...

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