Related Experiment Video
Updated: May 29, 2026
13:07
Determining 3'-Termini and Sequences of Nascent Single-Stranded Viral DNA Molecules during HIV-1 Reverse Transcription in Infected Cells
Published on: January 30, 2019
A widespread class of reverse transcriptase-related cellular genes
Eugene A Gladyshev1, Irina R Arkhipova
1Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
Summary
Researchers discovered a new class of cellular genes, named rvt, related to reverse transcriptases (RTs). These genes are widespread across life and encode proteins that can synthesize both RNA and DNA, challenging previous assumptions about RT-like enzymes.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Genetics
Background:
- Reverse transcriptases (RTs) are enzymes that synthesize DNA from RNA templates, typically associated with viruses and retrotransposons.
- Most RT-like enzymes are believed to be non-essential for host cells, with telomerases as a key exception.
- The functional and evolutionary roles of RNA-dependent polymerases in cellular organisms are not fully understood.
Purpose of the Study:
- To report the discovery and characterization of a novel class of RT-related cellular genes, designated rvt.
- To investigate the evolutionary origin, genomic characteristics, and biochemical properties of these newly identified genes and their protein products.
Main Methods:
- Bioinformatic analysis to identify and characterize rvt genes across diverse taxonomic groups.
- Phylogenetic analysis to determine evolutionary relationships and selection pressures.
- Biochemical assays to assess the enzymatic activity of purified RVT proteins in vitro.
Main Results:
- Identified a unique class of single-copy cellular genes (rvt) with conserved domain structures, introns, and evolutionary patterns.
- Demonstrated that rvt genes are present in a wide range of organisms, including protists, fungi, animals, plants, and bacteria.
- Showed that the purified RVT protein from Neurospora crassa polymerizes both NTPs and dNTPs, with a preference for NTPs, using Mn(2+) cofactor.
Conclusions:
- The discovery of rvt genes represents a previously unrecognized class of RT-related enzymes with potential roles in host cells.
- These findings necessitate a reevaluation of the evolutionary origins and functional significance of RNA-dependent polymerases in biology.
- The ability of RVT proteins to polymerize both RNA and DNA suggests diverse functional possibilities beyond the known roles of RTs.
Related Concept Videos
02:33Retroviruses
Retroviruses and retrotransposons both insert copies of their genetic elements into the genome of the host cell. Thus, the viral genes are passed on when the host genome is replicated or translated. A typical retroviral DNA sequence contains 3-4 genes that encode the different proteins required for its structural assembly and function as a molecular parasite. This DNA is transcribed into a single mRNA, which is very similar in structure to conventional mRNAs, i.e., it is capped at the 5’...
03:08LTR Retrotransposons
LTR retrotransposons are class I transposable elements with long terminal repeats flanking an internal coding region. These elements are less abundant in mammals compared to other class I transposable elements. About 8 percent of human genomic DNA comprises LTR retrotransposons. Some of the common examples of LTR retrotransposons are Ty elements in yeast and Copia elements in Drosophila.
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
The internal coding region of LTR retrotransposons and their mechanism of transposition closely resembles a...
03:18Non-LTR Retrotransposons
As the name suggests, non-LTR retrotransposons lack the long terminal repeats characteristic of the LTR retrotransposons. Additionally, both LTR and non-LTR retrotransposons use distinct mechanisms of mobilization. Non-LTR retrotransposons are further divided into two classes - Long interspersed nuclear elements (LINEs) and short interspersed nuclear elements (SINEs), both of which occur abundantly in most mammals, including humans. Some of the active non-LTR retrotransposons in humans are L1...
01:29Viruses with RNA Genomes
RNA viruses are categorized into positive-strand, negative-strand, or double-stranded groups based on their genomic structure and replication mechanisms. This classification dictates how they exploit host cellular machinery for protein synthesis and replication. Some RNA viruses also utilize reverse transcription as part of their life cycle, further diversifying their replication strategies.Positive-Strand RNA VirusesPositive-strand RNA viruses have genomes that function directly as messenger...
01:10Retrovirus Life Cycles
Retroviruses have a single-stranded RNA genome that undergoes a special form of replication. Once the retrovirus has entered the host cell, an enzyme called reverse transcriptase synthesizes double-stranded DNA from the retroviral RNA genome. This DNA copy of the genome is then integrated into the host’s genome inside the nucleus via an enzyme called integrase. Consequently, the retroviral genome is transcribed into RNA whenever the host’s genome is transcribed, allowing the retrovirus to...
01:26Size and Structure of Viral Genomes
Viral genomes exhibit remarkable diversity in size, structure, and composition, influencing their replication strategies and interactions with host cells. These genomes consist of either DNA or RNA and may be linear or circular. Additionally, they can be single-stranded or double-stranded, with each configuration affecting how the virus propagates within a host. RNA viruses, for instance, generally have smaller genomes than DNA viruses, a factor that contributes to their high mutation rates and...