Biomedical subjects

H R Rackwitz

Publications and source records attributed to H R Rackwitz.

24 records · Page 2Linked to original sources

PubMed1982

Synthesis and physicochemical properties of two analogs of poly(dA): poly(2-aminopurine-9-beta-D-deoxyribonucleotide) and poly 2-amino-deoxyadenylic acid.

Polymerization of chemically synthesized dn2h6ATP and dn2ATP by deoxynucleotidyl transferase from calf thymus furnished poly(dn2h6A) and poly(dn2A) respectively. The synthetic polynucleotides were characterized by spectroscopic, ultracentrifugation and enzymatic methods. In polynucleotide-polynucleotide interaction, poly(dn2h6A) and poly(dn2A) behaved like analogs of poly(dnA).

Animals↗

PubMed1982

Viroid RNA is accepted as a template for in vitro transcription by DNA-dependent DNA polymerase I and RNA polymerase from Escherichia coli.

The RNA genome of potato spindle tuber viroid (PSTV) is transcribed in vitro into complementary DNA and RNA by DNA-dependent DNA polymerase I and RNA polymerase, respectively, from Escherichia coli. In vitro synthesis of complementary RNA produces distinct transcripts larger than unit length thus reflecting the in vivo mechanism of viroid replication. The influence of varying experimental conditions on the transcription process is studied; actinomycin D is found to drastically reduce complementary RNA synthesis from the PSTV RNA template by RNA polymerase.

DNA Polymerase I↗

PubMed1981

DNA-dependent RNA polymerase II of plant origin transcribes viroid RNA into full-length copies.

DNA-dependent RNA polymerase II purified from healthy plant tissue is capable of synthesizing linear (-)-viroid RNA copies of full length from (+)-viroid RNA templates in vitro. Together with the specific alpha-amanitin sensitivity of viroid replication observed in vivo, these findings suggest that viroids replicate by an entirely novel mechanism in which infecting viroid RNA molecules are copied by the host enzyme which is normally responsible for the synthesis of nuclear precursors to messenger RNA.

Amanitins↗

PubMed1981

Specifically primed synthesis in vitro of full-length DNA complementary to potato-spindle-tuber viroid.

Potato spindle tuber viroid (PSTV) RNA is transcribed in vitro by reverse transcriptase into complementary DNA in the presence of synthetic oligodeoxyribonucleotides as primers. In the case of priming with the pentadecadeoxyribonucleotide d(T-T-C-T-T-T-T-T-T-C-T-T-T-T-C) complementary to PSTV RNA from nucleotides 49 to 63, specificity of transcription initiation allows rapid sequencing of part of the viroid genome using chain-terminating dideoxyribonucleoside triphosphates. The DNA transcripts obtained represent distinct molecular species with the largest product being a full-length copy of the viroid RNA template. Molecular hybridization with 32P-labeled complementary DNA detects sequence homologies among different viroid species.

Base Composition↗

PubMed1977

The stereochemical basis of template function.

The behavior of nucelotides with thioketo-substituted pyrimidine bases (4-thiouracil, 2-thiouracil and 2-thiocytosine) or amino-analogue purine bases (2-aminopurine and 2,6-diaminopurine) in transcription and translation was investigated. The experimental results obtained led to the following conclusions. 1. The stereochemical basis of substrate selection in transcription is the geometry of Watson-Crick base pairs A-U (or A-T) and G-C between substrate and template bases. 2. The topology of the active site of Escherichia coli RNA polymerase is precisely adopted to the geometry of Watson-Crick base pairs. 3. The enzyme active site discriminates between A-U (A-T) and G-C base pairs. An essential feature in this discrimination is the 6-NH2 group of the A-U (A-T) base pair and the 2-keto group of cytosine in the G-C base pair. 4. The codon properties of a nucleic acid base in messenger RNA can be predicted on the basis of its specificity in polynucleotide interactions. There seems to be no evidence for the participation of protein topological sites in the control of the specificity of codon-anticodon interactions in translation.

Animals↗

PubMedDate not supplied

Acetylation of the HIV-1 Tat protein by p300 is important for its transcriptional activity.

The human immunodeficiency virus 1 (HIV-1) Tat protein activates transcriptional elongation by recruiting the positive transcription elongation factor (pTEFb) complex to the TAR RNA element, which is located at the 5' extremity of all viral transcripts [1-3]. Tat also associates in vitro and in vivo with the transcriptional coactivator p300/CBP [4-6]. This association has been proposed to recruit the histone acetyltransferase (HAT) activity of p300 to the integrated HIV-1 promoter. We have observed that the purified p300 HAT domain acetylates recombinant Tat proteins in vitro and that Tat is acetylated in vivo. The major targets of acetylation by p300 are lysine residues (Lys50 and Lys51) in the arginine-rich motif (ARM) used by Tat to bind RNA and for nuclear import. Mutation of these residues in full-length recombinant Tat blocked its acetylation in vitro. Furthermore, mutation of these lysine residues to arginine markedly decreased the synergistic activation of he HIV promoter by Tat and p300 or by Tat and cyclin T1. These results demonstrate that acetylation of Tat by p300/CBP is important for its transcriptional activation of the HIV promoter.

Acetylation↗