RESUMO
The presence of transcripts for somatostatin receptor (SSTR) subtypes 1, 2, 3, and 4 was probed by reverse transcription and polymerase chain reaction in ribonucleic acid isolated from 46 malignant and 9 nonmalignant breast tissues, 15 carcinoid tumor tissues, and 13 renal cell carcinoma tissues. The transcripts for SSTR2 were amplified in all but 2 tissue samples, whereas transcripts for SSTR1, SSTR3, and SSTR4 were detected sporadically. In renal cell tumors, SSTR3 transcripts were completely absent. In breast cancer tissue, SSTR subtypes were transcribed independently of patient age, menstrual status, diagnosis, histological grade, and levels of estrogen receptor and progesterone receptor. The probability of finding transcripts for SSTR subtypes, P, was ranked differently for the three types of tumor tissues. For breast cancer, P2 > P3 = P1 > P4; for carcinoid tumors, P2 > P1 > P3 = P4; and for renal cell tumors, P2 > P1 > P4 > P3.
Assuntos
Neoplasias da Mama/metabolismo , Tumor Carcinoide/metabolismo , Carcinoma de Células Renais/metabolismo , Expressão Gênica , Neoplasias Renais/metabolismo , Receptores de Somatostatina/biossíntese , Adulto , Idoso , Idoso de 80 Anos ou mais , Sequência de Bases , Neoplasias da Mama/cirurgia , Tumor Carcinoide/cirurgia , Carcinoma de Células Renais/cirurgia , Primers do DNA , DNA Complementar , Feminino , Humanos , Neoplasias Renais/cirurgia , Menopausa , Pessoa de Meia-Idade , Dados de Sequência Molecular , Reação em Cadeia da Polimerase/métodos , RNA Neoplásico/isolamento & purificação , RNA Neoplásico/metabolismo , Transcrição GênicaRESUMO
The isolated ribonuclease (RNase) H domain of human immunodeficiency virus type 1 (HIV-1) is enzymatically inactive. The incorporation of the putative substrate binding site of Escherichia coli RNase HI (amino acid residues 76-102, the alpha c-helix and adjacent loop region) into the equivalent position of the RNase H domain of HIV-1 resulted in a highly active hybrid protein dependent on Mn2+. Similar restoration of RNase H activity has been observed when histidine residues are added to either the N- or C-terminus of the HIV-1 RNase H domain. The hybrid HIV-1/E. coli RNase H protein is approximately 10-fold more active than HIV-1 reverse transcriptase and 30-fold more active than the histidine-tagged proteins, indicating that the alpha c-helix and adjacent loop region of E. coli RNase HI is an excellent substrate binding region because of its sequence and/or location. The RNase H hybrid produced the same specific cleavage in the model tRNA(Lys3) primer removal assay as HIV-1 reverse transcriptase, showing that substrate binding and specificity are separable and that the specificity determinants are at least partially, if not totally, contained in the amino acid sequence of the hybrid protein derived from HIV-1 reverse transcriptase.