まとめ
人間のrasH遺伝子の突然変異により,その変異活性が著しく変化し,ほとんどの変異体は効能が増加した. 減少したGTP水解はすべての変異体で観察されたが,変換と直接相関することはなく,それが示唆された.
科学分野:
- 分子生物学は分子生物学である.
- 腫瘍遺伝子 (オンコゲネス) とは
- シグナルトランスデュークション.
背景:
- rasH遺伝子は,細胞の成長と分化に関与する原発がん遺伝子である.
- ラス遺伝子の変異は,ヒトの癌ではよく見られ,制御不能の細胞増殖につながります.
- rasHの機能を理解することは,がんの研究と治療の開発に不可欠です.
研究 の 目的:
- ヒトのrasH遺伝子のコードン61の特定のアミノ酸置換の機能的影響を調査する.
- rasH変換活性,p21発現レベル,GTPase活性との関係を決定する.
- ラス媒介細胞変異におけるGTP水解の役割を明らかにする.
主な方法:
- サイト指向型変異は,ヒトのrasH遺伝子のコードン61に17の異なるアミノ酸置換を導入するために使用されました.
- 変異した rasH タンパク質の変換活性が評価されました.
- 変異したp21タンパク質のグアニンヌクレオチド結合とGTP水解率を分析した.
主要な成果:
- 導入された17の変異のうち15の変異は,rasHの変異活性を増やし,その効力は1000倍以上変化した.
- 変異活性が低下した変異体は,変異のためにより高いp21発現レベルを必要とした.
- 変異タンパク質17種すべては,変異能力に関係なく,GTPの水解速度が著しく低下 (8〜10倍低い) している.
- 変異タンパク質のグアニンヌクレオチド結合特性は変化しませんでした.
結論:
- 減少したGTP水解は,rasH変異体の共通の特徴であるが,変異の可能性を与えるには不十分である.
- rasH変換活性の程度は,GTPase活性の低下と定量的に相関していません.
- これらの発見は,rasシグナル伝達の複雑さを強調し,他の要因がras媒介性腫瘍形成に寄与することを示唆しています.
関連する概念動画
Mutations
Overview
Translation
Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
The Ras Gene
The Ras-gene-encoded proteins are regulators of signaling pathways controlling cell proliferation, differentiation, or cell survival. The Ras-gene family in humans constitutes three primary members—the HRas, NRas, and KRas. These genes code for four functionally distinct yet closely related proteins—the HRas, NRas, KRas4A, and KRas4B. The involvement of mutant Ras genes in human cancer was first discovered in 1982 and is among the most common causes of human tumorigenesis.
Ras is a superfamily...
Ras is a superfamily...
Mutations
Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations can be characterized in a number of different ways: whether and how they alter the amino acid sequence of the protein, whether they occur over a small or large area of DNA, and whether they occur in somatic cells or germline cells.
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
Translation
Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of Life
Nucleotide Excision Repair
DNA Distortion and Damage
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...


