Disease relevance of PZF1

• High level expression in E. coli and purification of yeast transcription factor IIIA [1].

High impact information on PZF1

• Thus, TFIIIB is the sole transcription initiation factor of S. cerevisiae pol III; TFIIIC and TFIIIA are assembly factors for TFIIIB [2].
• In proteins possessing multiple zinc fingers, including TFIIIA, Sp1, SWI5 and oestrogen/glucocorticoid receptors, the region containing the zinc fingers confers DNA-binding specificity [3].
• Transcription factor IIIA (TFIIIA), the canonical zinc-finger protein, is a protein of relative molecular mass 39,000 (39K) that is required for transcription of 5S-ribosomal subunit genes in Xenopus [4].
• TFIIIA binds to DNA through its 30 K N-terminal domain, which contains nine zinc-fingers [4].
• The only essential function of TFIIIA in yeast is the transcription of 5S rRNA genes [5].

Biological context of PZF1

• Analysis of DNA upstream of the RPB6 gene revealed an open reading frame that predicts a protein, designated PZF1, with nine C2H2 zinc fingers [6].
• We found that purified recombinant PZF1 specifically binds the internal control region (ICR) of the 5S rRNA gene in S. cerevisiae [6].
• The PZF1 gene was found to be single copy, transcribed into a 1.5-kilobase mRNA, and essential for yeast cell viability [6].
• Interestingly, the yeast RPB6 and TFIIIA coding sequences are divergently transcribed and are separated by only 233 base pairs, providing the potential for coregulated expression of components of RNA polymerases and the 5S rRNA component of ribosomes [6].
• The site of RNA polymerase III transcription factor A (TFIIIA) binding, mapped by determination of the G residues that are protected from methylation on exposure of the TFIIIA.5 S DNA complex to dimethyl sulfate, is coincident with the ICR [7].

Anatomical context of PZF1

• This inhibition is diminished when 5 S rDNA is first incubated with the cell-free system, implying the presence of a transcription factor IIIA analog in yeast, and is dependent on the nucleotide sequence of the 5 S rRNA added [8].
• Characterization of the RNA binding properties of transcription factor IIIA of Xenopus laevis oocytes [9].

Associations of PZF1 with chemical compounds

• TFIIIA with internal deletions that removed residues 282 to 315, 316 to 334, 328 to 341, or 342 to 351 of the 81-amino-acid domain retained activity, whereas TFIIIA with a deletion of the short leucine-rich segment 352NGLNLLLN359 at the carboxyl-terminal end of this domain was devoid of activity [10].
• It was sensitive to phenol extraction and resistant to RNase, and its target did not appear to be transcription factor IIIA [11].
• In the fourth case, however, a substitution of phenylalanine for the wild-type leucine at position 148 in TFIIIA results in much larger compensating changes in the kinetics of complex assembly and dissociation [12].
• Transcription factors TFIIIA and TFIIIC are able to be stably sequestered onto 5SrDNA-cellulose, but factor TFIIIB is not able to associate with the 5SrDNA-TFIIIA-TFIIIC complex in the presence of novobiocin [13].

Other interactions of PZF1

• Instead, a complete transcription factor complex consisting of TFIIIA, TFIIIB, and TFIIIC needed to be formed before the addition of histones in order for the 5S chromatin to subsequently be transcribed by RNA polymerase III [14].
• We propose a model for the regulation of yeast 5 S rRNA synthesis in which YL3 competes with the presumptive transcription factor IIIA analog for binding of 5 S rRNA [8].
• This leads us to postulate that GAL4 does not possess a TFIIIA-like "Zn-finger" but forms a binuclear metal cluster involving all six cysteines in a "cloverleaf"-like array [15].

Analytical, diagnostic and therapeutic context of PZF1

• We have combined this genetic assay with a simple and efficient method of mutagenesis that makes use of error-prone PCR and homologous recombination to generate and screen large numbers of TFIIIA mutants for those with altered 5 S rRNA gene-binding affinity [16].

References