Small molecule–based targeting of TTD-A dimerization to control TFIIH transcriptional activity represents a potential strategy for anticancer therapy

Abstract

The human transcription factor TFIIH is a large complex composed of 10 subunits that form an intricate network of protein-protein interactions critical for regulating its transcriptional and DNA repair activities. The trichothiodystrophy group A protein (TTD-A or p8) is the smallest TFIIH subunit, shuttling between a free and a TFIIH-bound state. Its dimerization properties allow it to shift from a homodimeric state, in the absence of a functional partner, to a heterodimeric structure, enabling dynamic binding to TFIIH. Recruitment of p8 at TFIIH stabilizes the overall architecture of the complex, whereas p8's absence reduces its cellular steady-state concentration and consequently decreases basal transcription, highlighting that p8 dimerization may be an attractive target for down-regulating transcription in cancer cells. Here, using a combination of molecular dynamics simulations to study p8 conformational stability and a >3000-member library of chemical fragments, we identified small-molecule compounds that bind to the dimerization interface of p8 and provoke its destabilization, as assessed by biophysical studies. Using quantitative imaging of TFIIH in living mouse cells, we found that these molecules reduce the intracellular concentration of TFIIH and its transcriptional activity to levels similar to that observed in individuals with trichothiodystrophy owing to mutated Our results provide a proof of concept of fragment-based drug discovery, demonstrating the utility of small molecules for targeting p8 dimerization to modulate the transcriptional machinery, an approach that may help inform further development in anticancer therapies.

Cell-type specific concentration regulation of the basal transcription factor TFIIH in XPBy/y mice model

“…In this context, we have hypothesised that low sub-optimal TFIIH concentrations at the cellular level may play a protective role by greatly hindering the unscheduled proliferation of cells required during carcinogenesis. Ensuing this hypothesis, we recently designed two new drugs that interfere with the binding of the TTDA subunit to TFIIH (compounds 12 and 19 in [9]). The rationale behind this study was that cells from patient with mutated TTDA present a lower level of TFIIH [35] because of reduced stability of the TFIIH complex [10, 11].…”

“…The rationale behind this study was that cells from patient with mutated TTDA present a lower level of TFIIH [35] because of reduced stability of the TFIIH complex [10, 11]. Reducing the stability of TFIIH by treating cells with these drugs decreased the level of TFIIH and transcriptional activity [9]. In future studies, these types of destabilizing drugs will be evaluated in the context of carcinogenesis.…”

The Structures of Eukaryotic Transcription Pre-initiation Complexes and Their Functional Implications

“…In addition to its association with these inherited disorders, TFIIH has also been implicated in promoting cancer cell growth due to the transcription-promoting activity of its CAK module and the requirement for elevated transcription in cancer cells. Therefore, TFIIH is a possible drug target in cancer chemotherapy (Berico and Coin 2017;Fisher 2018;Gervais et al 2018).…”

Cell-type specific concentration regulation of the basal transcription factor TFIIH

“…In this context, we have hypothesised that low sub--optimal TFIIH concentrations at the cellular level may play a protective role by greatly hindering the unscheduled proliferation of cells required during carcinogenesis. Ensuing this hypothesis, we recently design two new drugs (compound 12 and 19) that interfere with the binding of the TTDA subunit to TFIIH(29). The rationale behind this study was that TTDA cells present a reduced level of TFIIH (30) and controls the stability of the TFIIH complex(2,31).…”

“…The rationale behind this study was that TTDA cells present a reduced level of TFIIH (30) and controls the stability of the TFIIH complex(2,31). Reducing the steady state level of TFIIH by treating cells with these drugs decreased the level of TFIIH and transcriptional activity(29) and will in the future be tested in the context of carcinogenesis. Surprisingly and remarkably, XPB concentration is tightly regulated in all cell types within tissues analysed in our study.…”