Viral And Cellular Factors Affecting Early Steps In HIV Reverse Transcription
Funder
National Health and Medical Research Council
Funding Amount
$465,750.00
Summary
One of the key events in the life cycle of HIV is the conversion of viral RNA into a double stranded DNA intermediate. This process, called reverse transcription, is carried out by the viral enzyme reverse transcriptase (RT) in conjunction with other viral and cellular factors. While HIV RT has been extensively studied and RT inhibitors have been used in anti-retroviral therapy for HIV patients, other viral and cellular factors essential for efficient HIV reverse transcription have not been prop ....One of the key events in the life cycle of HIV is the conversion of viral RNA into a double stranded DNA intermediate. This process, called reverse transcription, is carried out by the viral enzyme reverse transcriptase (RT) in conjunction with other viral and cellular factors. While HIV RT has been extensively studied and RT inhibitors have been used in anti-retroviral therapy for HIV patients, other viral and cellular factors essential for efficient HIV reverse transcription have not been properly investigated and may represent a new class of anti-HIV targets.This project, based on our long standing (>10 years) research interest and experience, aims at identification of the viral and cellular factors particularly involved in the early steps of HIV reverse transcription.We have obtained preliminary data which lead to hypotheses regarding what kind of viral and cellular factors might be involved and their possible modes of action. Experiments have been designed to specifically prove or disprove these hypotheses. Thus this project will help us achieve a more comprehensive understanding on how HIV uses other viral and cellular factors, in addition to RT, to accomplish one of the mandatory stage of its growth (reverse transcription); and identify viral and cellular factors which can be further explored as new targets for anti-retroviral therapy. This is particularly important, as HIV resistance to current drug therapy has emerged as one serious issue facing HIV patients, and the HIV care communities.Read moreRead less
During reverse transcription, the positive-strand HIV-1 RNA genome is converted into a double-stranded DNA copy which can be permanently insert into the host cell genome. Our laboratory and others have shown that reverse transcription requires a complex array of molecules, which includes the viral RNA. These RNA can be organised into elaborate structures that have only been partially defined. Genetic experiments have revealed that one of these RNA structures, called TAR, is required for optimal ....During reverse transcription, the positive-strand HIV-1 RNA genome is converted into a double-stranded DNA copy which can be permanently insert into the host cell genome. Our laboratory and others have shown that reverse transcription requires a complex array of molecules, which includes the viral RNA. These RNA can be organised into elaborate structures that have only been partially defined. Genetic experiments have revealed that one of these RNA structures, called TAR, is required for optimal initiation of reverse transcription (the first step of reverse transcription), but the precise mechanism is unknown. Recent advances in our laboratory have enabled a comprehensive study of the role played by TAR RNA in reverse transcription. Our leading hypotheses regarding the mechanism is required that TAR interacts with other RNA sequences or Reverse transcriptase in the initiation complex so that the reaction is optimal. This proposal will investigate these two leading hypotheses. Given the enormity of the HIV pandemic and the many recent reports from the United States that most patient isolated virus is resistant to at least one antiretroviral drug, these studies have as an outcome the identification and characterisation of important new key molecules towards which antiretroviral strategies can be designed.Read moreRead less
The Mechanism Of Tat-enhanced Reverse Transcription In HIV-1
Funder
National Health and Medical Research Council
Funding Amount
$282,750.00
Summary
During reverse transcription, the positive-strand HIV-1 RNA genome is converted into a double-stranded DNA copy which can be permanently insert into the host cell genome. Many HIV-1 proteins including Tat contribute to the efficiency of reverse transcription. There are two competing hypotheses to explain how Tat enhances reverse transcription. The indirect mechanism hypothesis holds that Tat-enhanced reverse transcription is due to the combined effects of the Tat-induced expression of cellular g ....During reverse transcription, the positive-strand HIV-1 RNA genome is converted into a double-stranded DNA copy which can be permanently insert into the host cell genome. Many HIV-1 proteins including Tat contribute to the efficiency of reverse transcription. There are two competing hypotheses to explain how Tat enhances reverse transcription. The indirect mechanism hypothesis holds that Tat-enhanced reverse transcription is due to the combined effects of the Tat-induced expression of cellular genes. The direct mechanism hypothesis is that Tat functions directly during RTN, implying it is a virion protein. Our recent genetic and biochemical data provide strong evidence that a novel form of Tat, which we call vTat, has a direct role in RTN. This proposal will investigate these two leading hypotheses. Given the enormity of the HIV pandemic and the many recent reports from the United States that most patient isolated virus is resistant to at least one antiretroviral drug, these studies have as an outcome the identification and characterisation of important new key molecules towards which antiretroviral strategies can be designed.Read moreRead less
Title: Structure of hepadnaviral pre-genomic RNA. We aim to study the replication strategy of human hepatitis B virus (HBV), a member of the hepadnavirus family. Hepadnaviruses infect hepatocytes in the liver and are released in high numbers into the bloodstream. Infection is transmitted by blood or sexual contact. Hepadnaviruses cause acute and chronic infection with varying degrees of liver disease. The HBV DNA genome is formed by copying of a viral pre-genome made of RNA, into DNA. This proce ....Title: Structure of hepadnaviral pre-genomic RNA. We aim to study the replication strategy of human hepatitis B virus (HBV), a member of the hepadnavirus family. Hepadnaviruses infect hepatocytes in the liver and are released in high numbers into the bloodstream. Infection is transmitted by blood or sexual contact. Hepadnaviruses cause acute and chronic infection with varying degrees of liver disease. The HBV DNA genome is formed by copying of a viral pre-genome made of RNA, into DNA. This process is called reverse transcription and is performed by the viral polymerase. Reverse transcription occurs within viral nucleocapsids made of core antigen. After formation of the new viral DNA genome, nucleocapsids are enveloped in surface antigen and are released from the cell. It is assumed that 1 copy of HBV pre-genomic RNA is packaged within each viral nucleocapsid. However, members of the retrovirus family that have common evolutionary origins to hepadnaviruses and also replicate via reverse transcription, contain 2 copies of RNA. The human immunodeficiency virus (HIV), the AIDS virus, is a well-studied example. In HIV infection 2 RNA genomes are packaged into each nucleocapsid and form a dimeric RNA genome. The HIV RNA is able to fold into a series of stem loops that promote formation of dimers. During the reverse transcription step in HIV replication, the polymerase switches templates and forms new combined strains of virus. The project aims to determine if 2 copies of pre-genomic RNA are packaged into HBV nucleocapsids. HBV pre-genomic RNA is able to form stem loop structures similar to those in HIV and has the potential to form dimeric RNA. If 2 copies of HBV pre-genomic RNA are packaged this will allow us to redefine the viral replication strategy and to develop a greater understanding of the relationships between hepadnaviruses and retroviruses. The formation of dimers will also provide a mechanism for recombination between HBV strains.Read moreRead less