Lanping Ma

Mutations in the basal transcription initiation/DNA repair factor TFIIH are responsible for three human disorders: xeroderma pigmentosum (XP), cockayne syndrome (CS) and trichothiodystrophy (TTD). The non-repair features of CS and TTD are thought to be due to a partial inactivation of the transcription function of the complex. To search for proteins whose interaction with TFIIH subunits is disturbed by mutations in patients we used the yeast two-hybrid system and report the isolation of a novel XPB interacting protein, SUG1. The interaction was validated in vivo and in vitro in the following manner. (i) SUG1 interacts with XPB but not with the other core TFIIH subunits in the two-hybrid assay. (ii) Physical interaction is observed in a baculovirus co-expression system. (iii) In fibroblasts under non-overexpression conditions a portion of SUG1 is bound to the TFIIH holocomplex as deduced from co-purification, immunopurification and nickel-chelate affinity chromatography using functional tagged TFIIH. Furthermore, overexpression of SUG1 in normal fibroblasts induced arrest of transcription and a chromatin collapse in vivo. Interestingly, the interaction was diminished with a mutant form of XPB, thus providing a potential link with the clinical features of XP-B patients. Since SUG1 is an integral component of the 26S proteasome and may be part of the mediator, our findings disclose a SUG1-dependent link between TFIIH and the cellular machinery involved in protein modelling/degradation.

Now cisplatin and its analogs are some of the most effective chemotherapeutic agents in clinical use as the first line of treatment in testicular and ovarian cancers. Unfortunately, they have several major drawbacks, such as cumulative toxicities of nephrotoxicity and ototoxicity, inherent or treatment-induced resistance. This has provided the motivation for developing novel metal complexes as anticancer agents with different mechanism of action. In recent years, significant attention has been devoted to the role of G-quadruplexes in cancer. It was found that the stabilization of G-quadruplexes by small molecules has been shown to inhibit the transcriptional activity of some oncogenes. Thus, the G-quadruplex motif has emerged as a promising target for the design of selective anticancer drugs. Apart from the purely organic heteroaromatic compounds reported as G-quadruplex binders, it has recently been shown that metal complexes can also interact strongly and selectively with quadruplex DNA and have potential anticancer activity. This review will highlight recent progress of the metal complexes as anticancer drugs targeting G-quadruplex DNA, and discuss their future potential in the medical fields. Considering the significant roles of the metal ions, the metal complexes will be discussed as follows: (1) Ruthenium(II) complexes; (2) Nickel(II) complexes; (3) Zinc(II) complexes; (4) Manganese(III) complexes; (5) Copper(II) complexes; (6) Palladium(II)/Platinum(II); (7) Other metal complexes.