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ÖZET BRCA1 GEN ÜRÜNÜNÜN HÜCRE İÇİNDEKİ LOKALİZASYONUNU İNCELENMEK İÇİN NON-İMMÜNOLOJİK BİR SİSTEMİN GELİŞTİRİLMESİ TOLGA ÇA?ATAY Yüksek Lisans Tezi, Moleküler Biyoloji ve Genetik Bölümü Tez Yöneticisi: Yardımcı Doçent. Dr. Işık G. Yuluğ Ağustos 1997, 92 sayfa Ailesel meme ve ovaryum kanserinden sorumlu olan BRCA1 geni klonlanmış ve meme ile ovaryum kanseri olan ailelerde genin ya mutasyona uğradığı yada kaybolduğu gösterilmiştir. BRCA1 geninin, tümör büyümesinde negatif düzenleyici olarak rol alan bir tümör baskılayıcı proteini kodladığı ileri sürülmüştür. BRCAİ'm biyolojik işlevinin incelenmesi için BRCA1 gen ürününün hücre içi yerinin belirlenmesini amaçlayan bazı çalışmalar yapılmıştır. Bu immünoflöresan/ immünohistokimyasal çalışmalardan elde edilen sonuçlar gen ürününün sitoplasmada veya hücre çekirdeğinde olduğuna dair iki karşıt görüş ortaya çıkarmıştır. Bizde, canlı hücrede immünolojik olmayan bir sistemde çalışarak BRCA1 gen ürününün hücre içerisindeki yerini tanımlıyoruz. Aequerea victorid nın yeşil flöresan protein (GFP) taşıyan proteinler, protein sentezin ve hedeflenmesinin canlı hücre içinde analizi için güçlü bir sistem sağlarlar. Bu yüzden GFP içeren füzyon proteinler canlı hücrede çekirdek trafiğini analiz etmede değerli bir araçtırlar. Bu çalışmada ökaryotik yeşil flöresan protein (EGFP) olarak bilinen bir çeşit mutant GFP' nin, memeli hücre çekirdeğine taşman bir proteininin işaretlenmesindeki kullanılımı rapor edilmiştir. BRCA1 proteinin beş adet çekirdek lokalizasyon sinyalini (NLSs) içeren parçasının EGFP ile birleştirilmesiyle yapılan kimerik proteinin canlı hücre içerisindeki davranışı incelenmiştir. Yapılan in vivo incelemenin sonucunda, EGFP'nin tek basma sentezlendiğinde sitoplazmaya ve çekirdeğe eşit bir şekilde dağıldığı gözlenmiştir. EGFP'nin BRCA1 proteinin NLSs içeren parçasıyla birleştirildiğinde flöresan sinyal dominant bir biçimde hücrenin çekirdeğinde tespit edilmesi ise bu NLSs sekanslarinin tam uzunliktaki BRCA1 proteinini hücre çekirdeğinde lokalize edebileceğini gösterilmiştir. Ayrıca bu çalışmada iv ABSTRACT DEVELOPMENT OF A NON-IMMUNOLOGICAL SYSTEM FOR THE STUDY OF THE CELLULAR LOCALIZATION OF BRCA1 GENE PRODUCT IN LIVING CELLS TOLGA ÇA?ATAY M. S. in Molecular Biology and Genetics Supervisor: Assist. Prof. Işık G. Yuluğ August 1997, 92 Pages BRCA1, is a familial breast and ovarian cancer susceptibility gene that has been cloned and shown to be either lost or mutated in families with breast and ovarian cancer. BRCA1, has been postulated to encode a tumor suppressor, a protein that acts as a negative regulator of tumor growth. To explore the biological function of BRCA1, several studies have been performed for the identification of cellular localization of BRCA1 gene product. Results obtained from these immunofluorescent/ immunohistochemical studies generated two opposing views, cytoplasmic localization versus nuclear localization. Here, we describe a non-immunological system employing the Eukaryotic Green fluorescent Protein (EGFP) tag for the study of the cellular localization of BRCA1 gene product in living cells. Proteins carrying the green fluorescent protein (GFP) of Aequorea victoria provide a powerful system to analyze protein expression and targeting in living cells. Fusion proteins containing the GFP tag are therefore valuable tools to analyze nuclear trafficking in living cells. Here, we reporte the use of a mutant GFP, namely Eukaryotic Green Fluorescent Protein (EGFP), as a marker for the protein import into mammalian nuclei. We have analyzed the behavior of a protein domain of the BRCA1, that contains five putative nuclear localization signals (NLSs), in vivo using a chimera constructed from this polypeptide and the EGFP. This in vivo studies showed that EGFP was distributed uniformly throughout the cytoplasm and the nucleus. When EGFP was fused to NLSs containing domain of the BRCA1 protein, fluorescent was predominantly detected in the nucleus, showing that these potential NLSs consensus sequences may destinate the full-lengh BRCA1 producy into the nucleus of mammalian cell. This study has also shown that EGFP can be used as a potential fluorescent tag for visualization of gene expression and cellular protein localization in living cells. Ill 107

Ankara : The Department of Molecular Biology and Genetics and the Institute of Graduate Studies of Bilkent University, 1997. Thesis (Master's) -- Bilkent University, 1997. Includes bibliographical references leaves 56-60. People bearing germline mutations in either BRCAl or BRCA2 genes are more prone to breast cancer than other people. These two recently identified genes account for nearly 90% of the hereditary cancer cases. This number corresponds approximately to 100,000 women each year in Turkey. The individuals who carry these mutations are at high risk and characterizing these mutations will be helpful for providing them genetic counseling. This includes the estimation of risk for both the individual and his/her progeny. In addition, discovering the mutations is an important step in finding out the iunctions of these genes, which will give insights about how breast cancer is occurring In this study, we have established an easy and rapid mutation detection strategy; heteroduplex analysis, and tested its efficiency in 15 hereditary breast cancer patients. These patients have been screened for the entire exon 11 of BRCAl, which is 50% o f the entire coding region. In addition, half of the exon 11 of BRCA2, which is roughly one fourth of the coding region was examined in 10 patients. As yet, no mutation in the Turkish patients have been encountered These results exclude exon 11 of the BRCAl gene and part of exon 11 of the BRCA2 gene for nucleotide deletions and insertions as the cause of hereditary breast cancer in Turkey. In order to verily the efficiency of the technique, we have also screened four French hereditary breast cancer patients with previously characterized BRCAl mutations in exon 11, and confirmed the presence o f the mutations in the majority o f the cases With the technique, firmly established in our laboratory, we plan to analyze the remaining coding regions of the BRCAl and BRCA2 genes in our patient samples and in additional patients. Öktem, Emre M.S.