Limits...
What contemporary viruses tell us about evolution: a personal view.

Moelling K - Arch. Virol. (2013)

Bottom Line: Viruses helped in building genomes and are driving evolution.Only in unbalanced situations do viruses cause infectious diseases or cancer.Are viruses our oldest ancestors?

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Molecular Genetics, Ihnestr 63-73, 14195, Berlin, Germany. moelling@imm.uzh.ch

ABSTRACT
Recent advances in information about viruses have revealed novel and surprising properties such as viral sequences in the genomes of various organisms, unexpected amounts of viruses and phages in the biosphere, and the existence of giant viruses mimicking bacteria. Viruses helped in building genomes and are driving evolution. Viruses and bacteria belong to the human body and our environment as a well-balanced ecosystem. Only in unbalanced situations do viruses cause infectious diseases or cancer. In this article, I speculate about the role of viruses during evolution based on knowledge of contemporary viruses. Are viruses our oldest ancestors?

Show MeSH

Related in: MedlinePlus

From RNA to DNA. (Top) This reaction is performed by the telomerase in every embryonic eukaryotic cell and in tumor cells at chromosomal ends. The telomerase is an RNP and copies a simple stretch of RNA into DNA up to 1000-fold. (Bottom) Reverse transcriptase (RT) copies RNA into an RNA-DNA hybrid and into a double-stranded DNA, supported by ribonuclease H (RNase H), which removes the RNA in RNA-DNA hybrids and RNA primers
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3755228&req=5

Fig3: From RNA to DNA. (Top) This reaction is performed by the telomerase in every embryonic eukaryotic cell and in tumor cells at chromosomal ends. The telomerase is an RNP and copies a simple stretch of RNA into DNA up to 1000-fold. (Bottom) Reverse transcriptase (RT) copies RNA into an RNA-DNA hybrid and into a double-stranded DNA, supported by ribonuclease H (RNase H), which removes the RNA in RNA-DNA hybrids and RNA primers

Mentions: How and when the transition from RNA to DNA occurred is a matter of speculation. DNA is much less multifunctional than RNA. DNA has a long-term memory and stabilizes genetic information, in contrast to the variable RNA. Deoxyribonucleotides may have formed without or with enzymes, such as a ribonucleotide reductase. In a protein world, the transition from RNA to DNA can possibly be witnessed today in embryonic and cancer cells, as well as in the replication of retro- and pararetroviruses. This transition occurs at the ends of chromosomes by telomerases in embryonic mammalian cells [8, 9] and in tumor cells [45]. The telomerases copy a short RNA sequence into DNA over and over again (Fig. 3). Telomerase is a specialized reverse transcriptase, a complex of an RNA-dependent DNA polymerase and an endogenous RNA. The RNA contains limited information, consisting solely of repeats of a few ribonucleotides, leading to the repeats at the telomeres of TTAAGGG or similar sequences in other species, which are repeated up to 1000 times, depending on the organism. Telomeric sequences protect genomes from losing information by shortening during replication. Watson and Crick already foresaw this problem when they first described the DNA double helix [111]. In adult cells, where the telomerases are inactive, insertion of telomerases can reverse aging and prevent death, as biotech companies are actively investigating. Telomerases can be detected in almost all forms of life. The telomeric structure of RNA/DNA in pseudoknots may be reminiscent of the pseudoknot structure of the RNA of some ribozymes. Whether there is an evolutionary relationship is not clear but may be worth analyzing [25, 29, 43, 44, 79].Fig. 3


What contemporary viruses tell us about evolution: a personal view.

Moelling K - Arch. Virol. (2013)

From RNA to DNA. (Top) This reaction is performed by the telomerase in every embryonic eukaryotic cell and in tumor cells at chromosomal ends. The telomerase is an RNP and copies a simple stretch of RNA into DNA up to 1000-fold. (Bottom) Reverse transcriptase (RT) copies RNA into an RNA-DNA hybrid and into a double-stranded DNA, supported by ribonuclease H (RNase H), which removes the RNA in RNA-DNA hybrids and RNA primers
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3755228&req=5

Fig3: From RNA to DNA. (Top) This reaction is performed by the telomerase in every embryonic eukaryotic cell and in tumor cells at chromosomal ends. The telomerase is an RNP and copies a simple stretch of RNA into DNA up to 1000-fold. (Bottom) Reverse transcriptase (RT) copies RNA into an RNA-DNA hybrid and into a double-stranded DNA, supported by ribonuclease H (RNase H), which removes the RNA in RNA-DNA hybrids and RNA primers
Mentions: How and when the transition from RNA to DNA occurred is a matter of speculation. DNA is much less multifunctional than RNA. DNA has a long-term memory and stabilizes genetic information, in contrast to the variable RNA. Deoxyribonucleotides may have formed without or with enzymes, such as a ribonucleotide reductase. In a protein world, the transition from RNA to DNA can possibly be witnessed today in embryonic and cancer cells, as well as in the replication of retro- and pararetroviruses. This transition occurs at the ends of chromosomes by telomerases in embryonic mammalian cells [8, 9] and in tumor cells [45]. The telomerases copy a short RNA sequence into DNA over and over again (Fig. 3). Telomerase is a specialized reverse transcriptase, a complex of an RNA-dependent DNA polymerase and an endogenous RNA. The RNA contains limited information, consisting solely of repeats of a few ribonucleotides, leading to the repeats at the telomeres of TTAAGGG or similar sequences in other species, which are repeated up to 1000 times, depending on the organism. Telomeric sequences protect genomes from losing information by shortening during replication. Watson and Crick already foresaw this problem when they first described the DNA double helix [111]. In adult cells, where the telomerases are inactive, insertion of telomerases can reverse aging and prevent death, as biotech companies are actively investigating. Telomerases can be detected in almost all forms of life. The telomeric structure of RNA/DNA in pseudoknots may be reminiscent of the pseudoknot structure of the RNA of some ribozymes. Whether there is an evolutionary relationship is not clear but may be worth analyzing [25, 29, 43, 44, 79].Fig. 3

Bottom Line: Viruses helped in building genomes and are driving evolution.Only in unbalanced situations do viruses cause infectious diseases or cancer.Are viruses our oldest ancestors?

View Article: PubMed Central - PubMed

Affiliation: Max Planck Institute for Molecular Genetics, Ihnestr 63-73, 14195, Berlin, Germany. moelling@imm.uzh.ch

ABSTRACT
Recent advances in information about viruses have revealed novel and surprising properties such as viral sequences in the genomes of various organisms, unexpected amounts of viruses and phages in the biosphere, and the existence of giant viruses mimicking bacteria. Viruses helped in building genomes and are driving evolution. Viruses and bacteria belong to the human body and our environment as a well-balanced ecosystem. Only in unbalanced situations do viruses cause infectious diseases or cancer. In this article, I speculate about the role of viruses during evolution based on knowledge of contemporary viruses. Are viruses our oldest ancestors?

Show MeSH
Related in: MedlinePlus