TI  - Cloning of two proximal sequence element-binding transcription factor
      subunits (gamma and delta) that are required for transcription of small
      nuclear RNA genes by RNA polymerases II and III and interact with the
      <prot>TATA-binding protein</prot>.
PG  - 1-9
AB  - The <prot>proximal sequence element (PSE)-binding transcription factor</prot> (<prot>PTF</prot>)
      specifically recognizes the PSEs of both RNA polymerase II- and RNA
      polymerase III-transcribed small nuclear RNA (snRNA) genes. We previously
      have shown that <prot>PTF</prot> purified from human HeLa cells is a multisubunit
      complex of four polypeptides designated  <prot><prot>PTF</prot> alpha</prot> ,  -beta ,  -gamma , and
       -delta . We now report the isolation and expression of cDNAs encoding <prot>PTF</prot>
      gamma and <prot>PTF</prot> delta, as well as functional studies with cognate antibodies
      that recognize the native <prot>PTF</prot> complex in HeLa extracts.
      Immunoprecipitation studies confirm that the four <prot>PTF</prot> subunits originally
      found to copurify during conventional chromatography indeed form a tightly
      associated complex; they further show that the <prot>PTF</prot> so defined, including
      the gamma and delta subunits specifically, is essential for transcription
      of both class II and class III snRNA genes. Immunoprecipitation assays
      also show a weak substoichiometric association of the  <prot>TATA-binding protein</prot>
      (<prot>TBP</prot>)  with  <prot>PTF</prot> , consistent with the previous report of a <prot>PTF</prot>-related
      complex (<prot>SNAPc</prot>) containing substoichiometric levels of <prot>TBP</prot> and a component
      (<prot>SNAPc43</prot>) identical in sequence to the <prot>PTF</prot> gamma reported here.
      Glutathione S-transferase pulldown assays further indicate relatively
      strong direct interactions of both recombinant  <prot>PTF</prot> gamma  and  <prot>PTF</prot> delta 
      with   <prot>TBP</prot>  , consistent either with the natural association of  <prot>TBP</prot>  with  <prot>PTF</prot> 
      in a semistable <prot>TBP</prot>-<prot>TBP</prot>-associated factor complex or with possible
      functional interactions between   PSE -bound  <prot>PTF</prot>   and   TATA -bound  <prot>TBP</prot>   during
      promoter activation. In addition, we show that in extracts depleted of <prot>TBP</prot>
      and <prot>TBP</prot>-associated factors, transcription from the U1 promoter is restored
      by recombinant <prot>TBP</prot> but not by <prot>TFIID</prot> or <prot>TFIIIB</prot>, indicating that
      transcription of class II snRNA genes requires a <prot>TBP</prot> complex different
      from the one used for mRNA-encoding genes.
AD  - Laboratory of Biochemistry and Molecular Biology, Rockefeller University,
