概括
超绕的 DNA 是一种超绕的 DNA.
科学领域:
- 分子生物学分子生物学
- 遗传学 是一个遗传学.
- 生物化学 生物化学
背景情况:
- DNA可以采用不同的螺旋形状,包括B型和Z型.
- B-螺旋形是标准的DNA结构,而Z-螺旋形是左手螺旋形.
- 某些DNA序列,如那些富含CG重复的序列,可以根据超级卷轴在这些形式之间过渡.
研究的目的:
- 研究DNA螺旋结构对大肠杆菌RNA聚合酶转录的影响.
- 为了确定CG丰富序列的Z-DNA构造是否阻碍了体外和体内转录.
主要方法:
- 在体外转录试验中,使用含有 (CG) 16 插入的超卷塑体进行了转录试验.
- 绘制S1核酶映射以分析来自大肠杆菌的体内转录.
- 通过CG序列的B-DNA与Z-DNA形式转录的比较.
- 测试d(CA) 21 X d(TG) 21插件作为控制器的影响.
主要成果:
- 在实验室中,大肠杆菌RNA聚合酶通过 (CG) 16序列以B螺旋形式转录.
- 当 (CG) 16 序列处于 Z-螺旋形状时,由于负超卷,转录被阻止.
- 在体内,大多数转录通过 (CG) 16 序列进行,表明它主要存在于 B-螺旋形式.
- 在类似的条件下,A d(CA) 21 X d(TG) 21插入物没有引起显著的转录阻塞.
结论:
- DNA的螺旋形状显著影响大肠杆菌RNA聚合酶的转录.
- 基因内的Z-DNA形成可以作为一种强大的转录阻断剂.
- 在体内,细胞机制可能会保持富含CG的B螺旋形式的序列,以允许转录.
相关概念视频
DNA Topoisomerases
Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
Cis-regulatory Sequences
Cis-regulatory sequences are short fragments of non-coding DNA that are present on the same chromosomes as the genes that they regulate. These fragments serve as binding sites for transcriptional regulators, proteins that are responsible for controlling gene transcription and differential gene expression across cell types in eukaryotes. Cis-regulatory sequences can be close to the gene of interest or thousands of bases away in the DNA sequence; however, those sequences that are further away are...
Eukaryotic Transcription Inhibitors
Certain biochemical processes, such as embryonic development and cell growth regulation, depend on the repression of specific genes. DNA binding proteins known as eukaryotic transcription inhibitors regulate the repression of gene expression in eukaryotes. The presence of these inhibitors at the required location and time in the cell is triggered by the presence of hormones and additional signals from other cells.
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
Eukaryotic transcription inhibitors usually contain two distinct domains, a DNA...
Transcription Attenuation in Prokaryotes
Transcriptional attenuation occurs when RNA transcription is prematurely terminated due to the formation of a terminator mRNA hairpin structure. Bacteria use these hairpins to regulate the transcription process and control the synthesis of several amino acids including histidine, lysine, threonine, and phenylalanine. Transcription attenuation takes place in the non-coding regions of mRNA.
There are several different mechanisms used to attenuate transcription. In ribosome mediated...
There are several different mechanisms used to attenuate transcription. In ribosome mediated...
Bacterial Transcription
RNA polymerase (RNAP) carries out DNA-dependent RNA synthesis in both bacteria and eukaryotes. Bacteria do not have a membrane-bound nucleus. So, transcription and translation occur simultaneously, on the same DNA template.
Transcription can be divided into three main stages, each involving distinct DNA sequences to guide the polymerase. These are:
Transcription can be divided into three main stages, each involving distinct DNA sequences to guide the polymerase. These are:
Cis-regulatory Sequences
Cis-regulatory sequences are short fragments of non-coding DNA that are present on the same chromosomes as the genes that they regulate. These fragments serve as binding sites for transcriptional regulators, proteins that are responsible for controlling gene transcription and differential gene expression across cell types in eukaryotes. Cis-regulatory sequences can be close to the gene of interest or thousands of bases away in the DNA sequence; however, those sequences that are further away are...


