TheXenopusu2 gene PSE is a single, compact, element required for transcription initiation and 3′ end formation

Abstract

The proximal sequence element (PSE) of a Xenopus U2 snRNA gene has been analysed by extensive local mutagenesis. The PSE is compact, lying between -61 and -50 bp upstream of the transcription start site and is involved in signalling both transcription initiation and 3' end formation. No PSE mutants were found in which these two activities were differentially affected. Analysis of U2 gene promoters mutant in both the PSE and DSE failed to reveal any evidence for multiple signals involved in 3' end formation, leading to the conclusion that the PSE is the only promoter element required for this function. The U2 and U6 PSEs, which direct either pol II or both pol II and pol III transcription respectively, are shown to be functionally interchangeable. Apparent differences in human and Xenopus U2 gene PSE structure are discussed.

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

“…Class II snRNA genes (e.g., U1 to U5) contain two regulatory elements in the 5Ј-flanking region: a distal sequence element (DSE) located approximately 220 bp upstream of the transcription start site, and a proximal sequence element (PSE) centered around Ϫ55. The DSE contains at least one copy of the octamer motif and functions as an upstream enhancer, whereas the PSE is an essential promoter element which functions in start site selection and may be required for accurate 3Ј-end formation (17,33,35). The promoters of class III snRNA genes (e.g., 7SK and U6) are located solely in the 5Ј-flanking region and lack intragenic control elements typical of most other class III genes (9, 29).…”

“…PSE swapping experiments between U2 and U6 genes have demonstrated that different PSEs are functionally interchangeable and per se are not responsible for polymerase selection (25,28,35). It is likely, therefore, that the transcription factor(s) bound to the PSE elements directly interacts with both class II and class III transcription factors to assist in RNA polymerase selection.…”

The differential transcriptional activity of two amphibian U1 small‐nuclear RNA genes correlates with structural differences in the proximal sequence element

“…The second, more proximal motif, is the PSE centered on -55. It specifies the transcription initiation site and is required for the formation of a stable transcription complex and snRNA 3' end in conjunction with a termination signal contained in the 3'-flanking regions (Dahlberg and Lund, 1988;Tebb and Mattaj, 1988;Parry et al, 1989aParry et al, , 1989b. Species-specific variation is observed at the sequence level of the PSE motif (Dahlberg and Lund, 1988) which shows, however, a large extent of sequence similarity among X .…”

“…Species-specific variation is observed at the sequence level of the PSE motif (Dahlberg and Lund, 1988) which shows, however, a large extent of sequence similarity among X . luevis snRNA genes, the best documented case reported by Parry et al (1989b).…”

“…The latter displays the best match with human U4C and mouse U6 PSEs. Sequences were from (1) Krol et al, (1985); (2) Parry et al, (1989b); (3) Carbon et al, (1987); (4) ; (5) Murphy et al,(3987); (6) Hernandez and Lucito (1988); (7) Bark et al, (1986); (8) Das et al, (1988) …”