Decreased expression and the Lys751Gln polymorphism of the XPD gene are associated with extreme longevity

Jacek Polosak Æ Malgorzata Roszkowska-Gancarz Æ Alina Kurylowicz Magdalena Owczarz Æ Paulina Dobosz Æ Malgorzata Mossakowska Æ Aleksandra Szybinska Æ Monika Puzianowska-Kuznicka

Received: 8 June 2009/Accepted: 13 August 2009/Published online: 26 August 2009  Springer Science+Business Media B.V. 2009

in blood mononuclear cells of people divided into three age groups (mean ages 28.7, 65.8 and 92.7 years old) showed that extreme longevity is associated with the decrease of the mean level of the specific mRNA; the differences between young or middle-aged vs. extremely old group were significant (P \ 0.0001, P \ 0.0001, respectively). In addition, the methylation pattern of the XPD promoter was analyzed in 30 people divided into three age groups (29.5, 65.9, and 101.4 years old). We showed that overall methylation of the XPD promoter is a rare event; however, aging is associated with the increase of methylation level upstream of the transcription start site. In summary, we showed for the first time that both the XPD polymorphic variants and the decreased level of its expression might be associated with aging.

mic instability. The XPD gene encodes a DNA helicase involved in nucleotide excision repair and in transcrip- tion. We analyzed the common XPD polymorphisms that were previously shown to affect protein’s DNA repair efficiency and to increase the risk of developing various cancers. Analysis was performed in 149 centenarians (mean age 101.1 years old) and in 413 young subjects (mean age 27.1 years old). We showed that the distribution of the Lys751Gln genotypes differed significantly between these groups (P = 0.017). In centenarians, the homozygous geno- types AA and CC were found less frequently than in young controls (29 vs. 36%, OR = 0.71, and 14 vs. 20%, OR = 0.652, respectively). The Arg156Arg and Asp312Asn were not significantly associated with extreme longevity. Analysis of the XPD mRNA level

J. Polosak    M. Roszkowska-Gancarz  P. Dobosz   M. Puzianowska-Kuznicka Department of Biochemistry and Molecular Biology, Medical Center of Postgraduate Education,

Marymoncka Street,

-

Warsaw, Poland

Introduction

Aging is a progressive, inevitable process affecting all human tissues. It depends on multiple environmental and endogenous factors, and, according to widely accepted theory, is a result of life-long accumulation of stochastic damage to the genomic DNA and to other

M. Owczarz  M. Mossakowska   A. Szybinska International Institute of Molecular and Cell Biology, 4 Trojdena Street, 02-109 Warsaw, Poland

an increased number of micronuclei and of chromo- somal aberrations compared to their young counter- parts (Burhans and Weinberger 2007; Kazim´ırova´ et al. 2009), we hypothesized that genes involved in the maintenance of genomic stability are involved in normal aging.

intra-cellular molecules such as key proteins and lipids (Terman and Brunk 2006; Petropoulos and Friguet 2006; Vin˜a et al. 2007; Hayflick 2007; Schumacher et al. 2008; Blagosklonny 2008; Afanas’ev 2009). Aging results in limiting the ability of the organism to maintain homeostasis, making it vulnerable to the development of different age-associated diseases such as diseases of the cardiovascular system, cancers and neurodegeneration (Taddei et al. 2006; Crews 2007; Jahangir et al. 2007; Ehrlich et al. 2008; Pietschmann et al. 2008; Andreassi 2008; Yankner et al. 2008).

by Sung and co-workers as a gene which result in cancer-prone xeroderma pigmen- type D (XPD) syndrome (Sung et al. 1993). gene is composed of 23 exons (Frederick et al. and encodes the xeroderma pigmentosum group D (XPD) protein which is a helicase that also possesses ATPase activity et al. 1993). XPD associates with transcription IIH (TFIIH), a multisubunit protein complex in RNA polymerase II transcription and in excision repair (NER) of genomic DNA (Sung et al. 1993; Go¨zu¨kara et al. 1994; et al. 1996; Cullinane et al. 1997; Evans al. 1997; Winkler et al. 2000). It also plays a role in apoptosis (Wang et al. 1996). Its result not only in the XPD syndrome, but in the XPD-Cockayne precocious aging syn- (XPD-CS) and in trichothiodystrophy (TTD), segmental progeria. However, disease phe- cannot be predicted from the position of residue. Crystal structure analysis of vari- mutated XPD molecules shed some light on this it seems that XPD mutations impair helicase activity, XPD-CS mutations alter activity and movements of Rad51/RecA-like domain 2, and TTD mutations impair TFIIH (Lehmann 2001; Lambert et al. 2008; Fan

It is estimated that genetic factors make up 25–30% of the causative agents of aging (McGue et al. 1993; Herskind et al. 1996; Finch and Ruvkun 2001). A number of genes have been identified as being involved, to various degrees, in regulating the aging process (Shimokawa et al. 2008; Slijepcevic 2008). These are, for example, genes encoding sirtuins (SIRT), a family of deacetylases modifying histones and other proteins such as transcription factors (Wood et al. 2004; Longo and Kennedy 2006; Kuningas et al. 2007; Milne and Denu 2008; Julien et al. 2009), genes encoding different elements of insulin and of insulin- like growth factor 1 pathways such as insulin and insulin-like growth factor 1 receptors, KLOTHO protein, and FOXO transcription factors (Kuro-O et al. 1997; Arking et al. 2002; Kurosu et al. 2005; DiStefano et al. 2007; Suh et al. 2008; Selman et al. 2008; Flachsbart et al. 2009; Bonafe` and Olivieri 2009), and genes the protein products of which, catalase and superoxide dismutases, are involved in the deactivation of reactive oxygen species (Hari et al. 1998; Parkes et al. 1998; Kirby et al. 2002; Blander et al. 2003; Landis and Tower 2005; Di Massimo et al. 2006; Paul et al. 2007).