A New Coactivator Function for Zac1's C₂H₂ Zinc Finger DNA-Binding Domain in Selectively Controlling PCAF Activity

Abstract

The generally accepted paradigm of transcription by regulated recruitment defines sequence-specific transcription factors and coactivators as separate categories that are distinguished by their abilities to bind DNA autonomously. The C 2 H 2 zinc finger protein Zac1, with an established role in canonical DNA binding, also acts as a coactivator. Commensurate with this function, p73, which is related to p53, is here shown to recruit Zac1, together with the coactivators p300 and PCAF, to the p21 Cip1 promoter during the differentiation of embryonic stem cells into neurons. In the absence of autonomous DNA binding, Zac1's zinc fingers stabilize the association of PCAF with p300, suggesting its scaffolding function. Furthermore, Zac1 regulates the affinities of PCAF substrates as well as the catalytic activities of PCAF to induce a selective switch in favor of histone H4 acetylation and thereby the efficient transcription of p21 Cip1 . These results are consistent with an authentic coactivator function of Zac1's C 2 H 2 zinc finger DNA-binding domain and suggest coactivation by sequencespecific transcription factors as a new facet of transcriptional control.The transcriptional activation of eukaryotic genes involves the regulated assembly of multiprotein complexes on enhancers and promoters (9,22,23). The specificity of this process is decisively controlled by sequence-specific DNA-binding transcription factors (henceforth termed "sequence-specific factors") which play a key role in interpreting and transmitting the information contained in the primary DNA sequence to the factors and cofactors that, in turn, mediate the synthesis of RNA transcripts from the DNA template.Sequence-specific factors typically contain a specific DNAbinding domain that directly contacts DNA, a multimerization domain that allows the formation of homo-or heteromultimers, and a transcription activation domain. The binding of sequencespecific factors to regulatory DNA elements, through which they are tethered to their correct location, is a prerequisite for gene regulation. This allows the positioning of the activation domain in the vicinity of the initiation complex and the subsequent recruitment of an active transcription complex (30). The sequential order of these events underlies the concept of gene activation via regulated recruitment (29).Sequence-specific factors that do not directly contact the basal transcription machinery often bind to different classes of interconnecting coregulators (for a minimal classification see reference 22).Among these, primary coactivators bind directly to sequence-specific factors and often contain relevant enzymatic activities that are necessary for changing chromatin structure from a quiescent state to one that permits active gene transcription; prototypical examples are the coactivators p300/CBP and PCAF, which are endowed with potent histone acetyltransferase (HAT) activities (21). In contrast, secondary coactivators dock onto sequence-specific factors and form a scaffold, thus facilitating the recruitm...

Transient Neonatal Diabetes Mellitus Gene Zac1 Impairs Insulin Secretion in Mice through Rasgrf1

“…The housekeeping gene for mitochondrial ATP synthase-coupling factor 6 (ATP5J) served for normalization. RNA extraction and qRT-PCR analysis were performed as described previously (17).…”

“…In addition to the context-dependent coregulation of nuclear receptors (19), p53, and p73 (17,18), Zac1 binds to different classes of DNA elements that determine transcriptional activator versus repressor activities (15)(16)(17).…”

Unbiased Screening for Transcriptional Targets of ZKSCAN3 Identifies Integrin β4 and Vascular Endothelial Growth Factor as Downstream Targets

“…Another possibility is that ZKSCAN3 modulates gene expression through a co-activator function, as does the C2H2 zinc finger protein Zac1. Zac1 stabilizes the interaction of p300 with pCAF, thus favoring histone H4 acetylation and gene transcription (54).…”

Zac1 Regulates Cell Cycle Arrest in Neuronal Progenitors via Tcf4

“…Tetracycline (Tc)-regulated Zac1 expression in C17.2 cells was established, and proliferation was measured as described previously (21,23). The mouse embryonic stem cell (ESC) line 46C was grown, and neuronal differentiation was performed as reported previously (25). In addition, cells were differentiated by treatment with all-trans retinoic acid (RA) (0.1 M) or by embryoid body (EB) formation as reported previously (26).…”