Signaling Pathways, Chemical and Biological Modulators of Nucleotide Excision Repair: The Faithful Shield against UV Genotoxicity
OXIDATIVE MEDICINE AND CELLULAR LONGEVITY
Authors: Kobaisi, F.; Fayyad, N.; Rezvani, H. R.; Fayyad-Kaza, M.; Sulpice, E.; Badran, B.; Fattad-Kazan, H.; Gidrol, X.; Rachidi, W.
Abstract
The continuous exposure of the human body's cells to radiation and genotoxic stresses leads to the accumulation of DNA lesions. Fortunately, our body has several effective repair mechanisms, among which is nucleotide excision repair (NER), to counteract these lesions. NER includes both global genome repair (GG-NER) and transcription-coupled repair (TC-NER). Deficiencies in the NER pathway underlie the development of several DNA repair diseases, such as xeroderma pigmentosum (XP), Cockayne syndrome (CS), and trichothiodystrophy (TTD). Deficiencies in GG-NER and TC-NER render individuals to become prone to cancer and neurological disorders, respectively. Therefore, NER regulation is of interest in fine-tuning these risks. Distinct signaling cascades including the NFE2L2 (NRF2), AHR, PI3K/AKT1, MAPK, and CSNK2A1 pathways can modulate NER function. In addition, several chemical and biological compounds have proven success in regulating NER's activity. These modulators, particularly the positive ones, could therefore provide potential treatments for genetic DNA repair-based diseases. Negative modulators, nonetheless, can help sensitize cells to killing by genotoxic chemicals. In this review, we will summarize and discuss the major upstream signaling pathways and molecules that could modulate the NER's activity.
Functional specialization of CK2 isoforms and characterization of isoform-specific binding partners
MOLECULAR AND CELLULAR BIOCHEMISTRY
Authors: Litchfield, DW; Bosc, DG; Canton, DA; Saulnier, RB; Vilk, G; Zhang, CJ
Abstract
In mammals, protein kinase CK2 has two isozymic forms of its catalytic subunit, designated CK2 alpha and CK2 alpha'. CK2 alpha and CK2 alpha' exhibit extensive similarity within their catalytic domains but have completely unrelated C-terminal sequences. To systematically examine the cellular functions of each CK2 isoform in mammalian cells, we have generated human osteosarcoma U2-OS cell lines with the expression of active or inactive versions of each CK2 isoform under the control of an inducible promoter [22]. Examination of these cell lines provides evidence for functional specialization of CK2 isoforms at the cellular level in mammals with indications that CK2 alpha' is involved in the control of proliferation and/or cell survival. To understand the molecular basis for functional differences between CK2 alpha and CK2 alpha', we have undertaken studies to identify proteins that interact specifically with each isoform of CK2 and could contribute to the regulation of their independent functions. A novel pleckstrin-homology domain containing protein, designated CK2-interacting protein 1 (i.e. CKIP-1) was isolated using the yeast two hybrid system as a protein that interacts with CK2 alpha but not CK2 alpha' [23]. When expressed in cells as a fusion with green fluorescent protein, CKIP-1 localizes to the cell membrane and to the nucleus. In this study, we present evidence from deletion analysis of CKIP-1 suggesting that a C-terminal region containing a putative leucine zipper has a role in regulating its nuclear localization. Collectively, our data supports a model whereby CKIP-1 is a non-enzymatic regulator of CK2 alpha that regulates the cellular functions of CK2 alpha by targeting or anchoring CK2 alpha to specific cellular localization or by functioning as an adapter to integrate CK2 alpha -mediated signaling events with components of other signal transduction pathways.