Gene Functional Classification
SUP
1)Metallothinein (MT) - MT1F, MT1M, MT1E, MT2A, MT1G, MT1B, MT4, MT1X, MT1H, and MT1A
MT is low molecular weight (7kDa), heat-stable and metal binding protein. The human genome includes a large set of MT genes belong to four families (MT1, MT2, MT3, and MT4), which collectively encode ten MT isoform proteins. Zn is the primary physiological inducer of MTs which play an important regulatory role in Zn uptake, distribution, storage, and release (Coyle et al. 2002). MTs increase in ageing process and show preferential binding with Zn in the aged people (Hamer 1986; Mocchegiani et al. 2000). High MTs levels and low Zn ion bioavailability are present in ageing and stress, and make the old susceptible to age-related degenerative diseases such as cancer and infection (Mocchegiani et al. 2000; Mocchegiani et al. 1997). Therefore Zn and MT homeostasis is crucial for immune response (Mocchegiani et al. 1998; Mocchegiani et al. 2000; Mocchegiani et al. 1997). Among MTs in the enrichment cluster, the physical interaction of MT2A with SPINK7 (ECRG2, Serine peptidase inhibitor, Kazal type 7) and with CXorf40A (EOLA1, endothelial-overexpressed lipopolysaccharide-associated factor1) may play an important role in the carcinogenesis of esophageal cancer and in the inflammation reaction respectively (Cui et al. 2003; Liang and Yang 2004). The polymorphism (+838C/G)of MT2A seems to influence inflammatory markers, zinc availability, NK cell cytotoxicity, and trace element status, all of which may promote carotid artery stenosis (CS) development in elderly people (Giacconi et al. 2007). The polymorphism (+647A/C) in the human MT1A gene affected the intracellular zinc ion release from the proteins which was associated with longevity in Italian population, and also showed that MT1A gene acted to control zinc-regulated gene expression in ageing with IL6 (interleukin6) (Cipriano et al. 2006; Mazzatti et al. 2008).
2)ATP-binding and ribosomal proteins
The lack of Zinc caused by starvation or by Zn chelation leads cells to death called apoptosis(Stefanidou et al. 2006). Apoptosis is induced by several extracellular or intracellular stimuli with an important role for trace metals like Zn or calcium(Seve et al. 2002). Zn depletion activates some apoptosis-specific proteases (caspases) that may activate the apoptotic endonucleases (Beyersmann 2002). NLRP10 (NLR family, pyrin domain containing 10) in the second enrichment group is a novel regulator of apoptosis and inflammation. NLRP10 binds to an adaptor protein that plays a role in apoptotic and inflammatory signal transduction, and to caspase-1 and IL-beta (Wang et al. 2004). The overexpression of Ribosomal protein S7 (RPS7) increases p53 activities, induces apoptosis and inhibits cell proliferation (Chen et al. 2007). RPS13 promote MDR (multidrug resistance) in gastric cancer cells by suppressing drug-induced apoptosis (Shi et al. 2004).
3)Kinesin super family proteins (KIFs) and Zinc finger proteins
KIFs play roles in the intracellular transport system, which is essential for cellular function and morphology. There is no direct evidence of the interaction between KIFs and Zn but they seem to indirectly interact with zinc finger proteins, which required Zn to stabilize their folds. KIF26B (kinesine-11 family) that are involved in signal transduction and regulate adhesion of the embryonic kidney mesenchyme is the downstream target of zinc finger protein, sall1, which is essential for ureteric bud attraction toward the messenchyme(Nishinakamura et al. 2010). Zinc finger proteins occur in nature as the part of transcription factors conferring DNA sequence specificity as the DNA-binding domain. MTF2 (metal response element binding transcription factor2) in the last group is known to zinc-dependently bind to the metal-regulating-element (MRE) of metallothionein-1A (MT1A) gene promoter (Inouye et al. 1994). There are many other kinesine super family and zinc finger protein members were included in the last two groups but the function of most member were still unknown. However, they seemed to have the possibility to directly or indirectly work with Zn for homeostasis, immune responses, apoptosis, and ageing.
SUB
1)Keratin associated proteins (KRTRP)
Keratin and KAP expression in human hair follicles were known to be affected by ageing processes. KRTAP4-2, 4-3, 4-4, 4-7, 4-9, and 9-8 that were identified in this study have been reported to be down-regulated significantly in aged hair follicles (Giesen et al. 2011). Keratins detected in this study appeared to be more related to cornea than skin and hair, although the function of most keratin family in this group was still unknown. Keratin12 (KRT12) is a representative cornea specific keratin genes and a missense mutation in the gene expressed the Meesmann’s corneal dystrophy. In addition to keratins, there is a non-keratin gene, BFSP2 (Beaded filament structural protein2). A deletion mutation of the BFSP2 was associated with the cataract formation in Chinese pedigree (Cui et al. 2007). Cataract is one of major causes for vision impairment and blindness worldwide and strongly related with age (Fletcher 2010). This analysis suggested that gene enriched in the clusters seemed to be involved in kinds of phenotypes related to ageing processes.
WHR
We found one significant gene enrichment group. Genes in this group seemed to be related with male fertility. A reduction of TNP2 (transition protein2) transcript was associated with asthebozoospermia(Jedrzejczak et al. 2007). PRM2 (protamine 2) is one of the major DNA-binding proteins in the nucleus of sperm and the expression level was reduced in azoospermic men (Friel et al. 2002). SNP analysis in the PRM1 and PRM2 genes was associated with the capability of fertilization in male populations (Tanaka et al. 2003). H2BFWT (H2B histone family, member W, testis-specific) is specifically expressed in sper nuclei and a polymorphism in the 5’ UTR is associated with male infertility (Lee et al. 2009).
Refernces
Beyersmann D (2002) Homeostasis and cellular functions of zinc. Materialwissenschaft Und Werkstofftechnik 33: 764-769.
Chen D, Zhang Z, Li M, Wang W, Li Y, Rayburn ER, Hill DL, Wang H, Zhang R (2007) Ribosomal protein S7 as a novel modulator of p53-MDM2 interaction: binding to MDM2, stabilization of p53 protein, and activation of p53 function. Oncogene 26: 5029-37.
Cipriano C, Malavolta M, Costarelli L, Giacconi R, Muti E, Gasparini N, Cardelli M, Monti D, Mariani E, Mocchegiani E (2006) Polymorphisms in MT1a gene coding region are associated with longevity in Italian Central female population. Biogerontology 7: 357-65.
Coyle P, Philcox JC, Carey LC, Rofe AM (2002) Metallothionein: the multipurpose protein. Cell Mol Life Sci 59: 627-47.
Cui X, Gao L, Jin Y, Zhang Y, Bai J, Feng G, Gao W, Liu P, He L, Fu S (2007) The E233del mutation in BFSP2 causes a progressive autosomal dominant congenital cataract in a Chinese family. Mol Vis 13: 2023-9.
Cui Y, Wang J, Zhang X, Lang R, Bi M, Guo L, Lu SH (2003) ECRG2, a novel candidate of tumor suppressor gene in the esophageal carcinoma, interacts directly with metallothionein 2A and links to apoptosis. Biochem Biophys Res Commun 302: 904-15.
Fletcher AE (2010) Free radicals, antioxidants and eye diseases: evidence from epidemiological studies on cataract and age-related macular degeneration. Ophthalmic Res 44: 191-8.
Friel A, Houghton JA, Glennon M, Lavery R, Smith T, Nolan A, Maher M (2002) A preliminary report on the implication of RT-PCR detection of DAZ, RBMY1, USP9Y and Protamine-2 mRNA in testicular biopsy samples from azoospermic men. Int J Androl 25: 59-64.
Giacconi R, Muti E, Malavolta M, Cipriano C, Costarelli L, Bernardini G, Gasparini N, Mariani E, Saba V, Boccoli G, Mocchegiani E (2007) The +838 C/G MT2A polymorphism, metals, and the inflammatory/immune response in carotid artery stenosis in elderly people. Mol Med 13: 388-95.
Giesen M, Gruedl S, Holtkoetter O, Fuhrmann G, Koerner A, Petersohn D (2011) Ageing processes influence keratin and KAP expression in human hair follicles. Exp Dermatol 20: 759-61.
Hamer DH (1986) Metallothionein. Annu Rev Biochem 55: 913-51.
Inouye C, Remondelli P, Karin M, Elledge S (1994) Isolation of a cDNA encoding a metal response element binding protein using a novel expression cloning procedure: the one hybrid system. DNA and Cell biology 13: 731-742.
Jedrzejczak P, Kempisty B, Bryja A, Mostowska M, Depa-Martynow M, Pawelczyk L, Jagodzinski PP (2007) Quantitative assessment of transition proteins 1, 2 spermatid-specific linker histone H1-like protein transcripts in spermatozoa from normozoospermic and asthenozoospermic men. Arch Androl 53: 199-205.
Lee J, Park HS, Kim HH, Yun YJ, Lee DR, Lee S (2009) Functional polymorphism in H2BFWT-5'UTR is associated with susceptibility to male infertility. J Cell Mol Med 13: 1942-51.
Liang Z, Yang Z (2004) Identification and characterization of a novel gene EOLA1 stimulating ECV304 cell proliferation. Biochem Biophys Res Commun 325: 798-802.
Mazzatti DJ, Malavolta M, White AJ, Costarelli L, Giacconi R, Muti E, Cipriano C, Powell JR, Mocchegiani E (2008) Effects of interleukin-6 -174C/G and metallothionein 1A +647A/C single-nucleotide polymorphisms on zinc-regulated gene expression in ageing. Exp Gerontol 43: 423-32.
Mocchegiani E, Muzzioli M, Cipriano C, Giacconi R (1998) Zinc, T-cell pathways, aging: role of metallothioneins. Mechanisms of Ageing and Development 106: 183-204.
Mocchegiani E, Muzzioli M, Giacconi R (2000) Zinc and immunoresistance to infection in aging: new biological tools. Trends Pharmacol Sci 21: 205-8.
Mocchegiani E, Verbanac D, Santarelli L, Tibaldi A, Muzzioli M, Radosevic-Stasic B, Milin C (1997) Zinc and metallothioneins on cellular immune effectiveness during liver regeneration in young and old mice. Life Sci 61: 1125-45.
Nishinakamura R, Uchiyama Y, Sakaguchi M, Terabayashi T, Inenaga T, Inoue S, Kobayashi C, Oshima N, Kiyonari H, Nakagata N, Sato Y, Sekiguchi K, Miki H, Araki E, Fujimura S, Tanaka SS (2010) Kif26b, a kinesin family gene, regulates adhesion of the embryonic kidney mesenchyme. Proceedings of the National Academy of Sciences of the United States of America 107: 9240-9245.
Seve M, Chimienti F, Favier A (2002) [Role of intracellular zinc in programmed cell death]. Pathol Biol (Paris) 50: 212-21.
Shi Y, Zhai H, Wang X, Han Z, Liu C, Lan M, Du J, Guo C, Zhang Y, Wu K, Fan D (2004) Ribosomal proteins S13 and L23 promote multidrug resistance in gastric cancer cells by suppressing drug-induced apoptosis. Exp Cell Res 296: 337-46.
Stefanidou M, Maravelias C, Dona A, Spiliopoulou C (2006) Zinc: a multipurpose trace element. Archives of Toxicology 80: 1-9.
Tanaka H, Miyagawa Y, Tsujimura A, Matsumiya K, Okuyama A, Nishimune Y (2003) Single nucleotide polymorphisms in the protamine-1 and -2 genes of fertile and infertile human male populations. Mol Hum Reprod 9: 69-73.
Wang YT, Hasegawa M, Imamura R, Kinoshita T, Kondo C, Konaka K, Suda T (2004) PYNOD, a novel Apaf-1/CED4-like protein is an inhibitor of ASC and caspase-1. International Immunology 16: 777-786.