Sandbox Reserved 967: Difference between revisions
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There are two types of RNase H (RNases H1 and RNases H2) classified according to their sequence conservation and substrate preference. Currently, three types of RNA/DNA hybrids are known: simple RNA/DNA duplexes ('''Figure 1A'''), RNA•DNA/DNA hybrids ('''Figure 1B'''), and DNA•RNAfew•DNA/DNA hybrids ('''Figure 1C'''). RNases H2 is totally able to cleave a single ribonucleotide embedded in a double strand DNA (DNA• RNAfew •DNA/DNA type) when RNases H1 require at least 4 ribonucleotides. This ability and their high expression in proliferating cells suggest that RNases H2 are involved in DNA repair and replication. | There are two types of RNase H (RNases H1 and RNases H2) classified according to their sequence conservation and substrate preference. Currently, three types of RNA/DNA hybrids are known: simple RNA/DNA duplexes ('''Figure 1A'''), RNA•DNA/DNA hybrids ('''Figure 1B'''), and DNA•RNAfew•DNA/DNA hybrids ('''Figure 1C'''). RNases H2 is totally able to cleave a single ribonucleotide embedded in a double strand DNA (DNA• RNAfew •DNA/DNA type) when RNases H1 require at least 4 ribonucleotides. This ability and their high expression in proliferating cells suggest that RNases H2 are involved in DNA repair and replication. | ||
[[Image: | [[Image:ProteopediaFigure1.jpg|300px|left|thumb]] | ||
''Manque figure, à ajouter...'' | |||
Indeed, ribonucleotides are wrongly incorporated into DNA during DNA replication at a frequency of about 2 ribonucleotides per kb. With such frequency, these errors are by far the most abundant threat of DNA damaging. Hence, a correction is essential to the preservation of DNA integrity: the most common correction mechanism involves RNases H2 and is called Ribonucleotide Excision Repair (RER). The incorporation of ribonucleotides in DNA produce DNA•RNAfew•DNA/DNA hybrids from which the few misincorporated ribonucleotides can be removed by an RNase H2. | Indeed, ribonucleotides are wrongly incorporated into DNA during DNA replication at a frequency of about 2 ribonucleotides per kb. With such frequency, these errors are by far the most abundant threat of DNA damaging. Hence, a correction is essential to the preservation of DNA integrity: the most common correction mechanism involves RNases H2 and is called Ribonucleotide Excision Repair (RER). The incorporation of ribonucleotides in DNA produce DNA•RNAfew•DNA/DNA hybrids from which the few misincorporated ribonucleotides can be removed by an RNase H2. | ||
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=== A heteromeric complex === | === A heteromeric complex === | ||
It has been shown that the Mammalian RNase complex is a heteromeric complex formed by 3 distinct proteins: H2A, H2B and H2C. H2A protein is the catalytic subunit and H2B/H2C proteins are auxiliary subunits: they are structural domains that facilitate cohesion of the complex. | It has been shown that the Mammalian RNase complex is a heteromeric complex formed by 3 distinct proteins: <scene name='60/604486/H2a/1'>H2A</scene>, H2B and H2C. H2A protein is the catalytic subunit and H2B/H2C proteins are auxiliary subunits: they are structural domains that facilitate cohesion of the complex. | ||
The first domain structure of the complex, H2A, contains 301 amino acids, almost as H2B protein which computes 308 amino acids. H2C protein is the smallest subunit: it only has 166 amino acids. | The first domain structure of the complex, H2A, contains 301 amino acids, almost as H2B protein which computes 308 amino acids. H2C protein is the smallest subunit: it only has 166 amino acids. | ||
Each of these proteins adopts various secondary structures with β-strands and α-helices: | Each of these proteins adopts various secondary structures with β-strands and α-helices: | ||
