scholarly journals The octamer-binding proteins Oct-1 and Oct-2 repress the HIV long terminal repeat promoter and its transactivation by Tat

1997 ◽  
Vol 322 (1) ◽  
pp. 155-158 ◽  
Author(s):  
Yu-Zhen LIU ◽  
David S. LATCHMAN
Keyword(s):  
Long Terminal Repeat ◽  
T Cell Activation ◽  
Cell Activation ◽  
Transcriptional Start Site ◽  
Cell Types ◽  
Inhibitory Effect ◽  
Terminal Repeat ◽  
Tat Protein ◽  
Different Cell Types ◽  
Hiv 1

Although the HIV-1 long terminal repeat (LTR) contains four potential binding sites for the octamer-binding protein, Oct-1, which is known to interact with the HIV-1 Tat protein, the effect of the Oct-1 factor on HIV LTR-driven gene expression has not previously been reported. We show here that both Oct-1, and to a lesser extent the related Oct-2 protein, can repress both the basal activity of the HIV-1 LTR and its transactivation by Tat. These effects are still observed with an HIV LTR construct containing only a single octamer-binding site located between the TATA box and the transcriptional start site. The stronger inhibitory effect of Oct-1 on both these promoters is dependent upon its C-terminal region which cannot be effectively replaced by the equivalent region of Oct-2. These effects are discussed in terms of the regulation of HIV LTR activity in different cell types and in response to T-cell activation.

scholarly journals APOBEC3G: an intracellular centurion

2008 ◽  
Vol 364 (1517) ◽  
pp. 689-703 ◽  
Author(s):  
Ya-Lin Chiu ◽  
Warner C Greene
Keyword(s):  
T Cells ◽  
Molecular Mass ◽  
T Cell Activation ◽  
Cd4 T Cells ◽  
Cell Activation ◽  
Protein Complexes ◽  
Biological Activities ◽  
Cell Types ◽  
Highly Active ◽  
Hiv 1

The intrinsic antiretroviral factor APOBEC3G (A3G) is highly active against HIV-1 and other retroviruses. In different cell types, A3G is expressed in high-molecular-mass (HMM) RNA–protein complexes or low-molecular-mass (LMM) forms displaying different biological activities. In resting CD4 T cells, a LMM form of A3G potently restricts HIV-1 infection soon after virion entry. However, when T cells are activated, LMM A3G is recruited into HMM complexes that include Staufen-containing RNA granules. These complexes are probably nucleated by the induced expression of Alu/hY retroelement RNAs that accompany T-cell activation. HMM A3G sequesters these retroelement RNAs away from the nuclear long interspersed nuclear element-derived enzymes required for Alu/hY retrotransposition. Human immunodeficiency virus (HIV) exploits this ‘window of opportunity’ provided by the loss of LMM A3G in activated CD4 T cells to productively infect these cells. During HIV virion formation, newly synthesized LMM A3G is preferentially encapsidated but only under conditions where Vif is absent and thus not able to target A3G for proteasome-mediated degradation. Together, these findings highlight the discrete functions of the different forms of A3G. LMM A3G opposes the external threat posed by exogenous retroviruses, while HMM A3G complexes oppose the internal threat posed by the retrotransposition of select types of retroelements.

Tissue-specific lability and expression of avian leukosis virus long terminal repeat enhancer-binding proteins

1989 ◽  
Vol 9 (12) ◽  
pp. 5660-5668 ◽  
Author(s):  
A Ruddell ◽  
M L Linial ◽  
M Groudine
Keyword(s):  
B Cells ◽  
Long Terminal Repeat ◽  
Binding Proteins ◽  
Cell Types ◽  
Avian Leukosis Virus ◽  
Terminal Repeat ◽  
Chromatographic Behavior ◽  
Heat Denaturation ◽  
Tissue Specific ◽  
Different Cell Types

Avian leukosis virus (ALV) induces bursal lymphomas in chickens, after proviral integration next to the cellular myc proto-oncogene, and subsequent c-myc hyperexpression. Our previous work suggested that labile or short-lived cellular proteins interact with the viral long terminal repeat (LTR) enhancer, and binding of these proteins appeared to be essential for high rates of LTR-enhanced transcription (A. Ruddell, M. Linial, W. Schubach, and M. Groudine, J. Virol. 62:2728-2735, 1988). This lability is specific for B-lymphoid cell types, since T cells and fibroblasts show stable high rates of LTR-enhanced transcription and stable LTR-binding activity. Moreover, the lability of these proteins may be important in determining susceptibility to bursal lymphoma. In this study, we separated and characterized the labile and stable LTR-binding proteins and examined their lability and expression in different cell types. Gel shift and DNase I footprinting analyses indicated that at least five proteins interact with the 140-base-pair LTR enhancer region. These proteins were distinct by several criteria, including lability or stability after inhibition of protein synthesis, resistance to heat denaturation, chromatographic behavior, and expression in different cell types. Two binding proteins were present in many cell types and were specifically labile in B cells. A third binding protein showed hematopoietic-cell-type-specific expression and was also labile in B cells. These findings indicate that there is tissue-specific modulation of the lability and expression of ALV LTR-binding proteins, which may be important for regulation of LTR transcription enhancement and ALV bursal lymphomagenesis.

scholarly journals Tissue-specific lability and expression of avian leukosis virus long terminal repeat enhancer-binding proteins.

1989 ◽  
Vol 9 (12) ◽  
pp. 5660-5668 ◽  
Author(s):  
A Ruddell ◽  
M L Linial ◽  
M Groudine
Keyword(s):  
B Cells ◽  
Long Terminal Repeat ◽  
Binding Proteins ◽  
Cell Types ◽  
Avian Leukosis Virus ◽  
Terminal Repeat ◽  
Chromatographic Behavior ◽  
Heat Denaturation ◽  
Tissue Specific ◽  
Different Cell Types

Avian leukosis virus (ALV) induces bursal lymphomas in chickens, after proviral integration next to the cellular myc proto-oncogene, and subsequent c-myc hyperexpression. Our previous work suggested that labile or short-lived cellular proteins interact with the viral long terminal repeat (LTR) enhancer, and binding of these proteins appeared to be essential for high rates of LTR-enhanced transcription (A. Ruddell, M. Linial, W. Schubach, and M. Groudine, J. Virol. 62:2728-2735, 1988). This lability is specific for B-lymphoid cell types, since T cells and fibroblasts show stable high rates of LTR-enhanced transcription and stable LTR-binding activity. Moreover, the lability of these proteins may be important in determining susceptibility to bursal lymphoma. In this study, we separated and characterized the labile and stable LTR-binding proteins and examined their lability and expression in different cell types. Gel shift and DNase I footprinting analyses indicated that at least five proteins interact with the 140-base-pair LTR enhancer region. These proteins were distinct by several criteria, including lability or stability after inhibition of protein synthesis, resistance to heat denaturation, chromatographic behavior, and expression in different cell types. Two binding proteins were present in many cell types and were specifically labile in B cells. A third binding protein showed hematopoietic-cell-type-specific expression and was also labile in B cells. These findings indicate that there is tissue-specific modulation of the lability and expression of ALV LTR-binding proteins, which may be important for regulation of LTR transcription enhancement and ALV bursal lymphomagenesis.

scholarly journals Targeting Aging: Lessons Learned From Immunometabolism and Cellular Senescence

2021 ◽  
Vol 12 ◽  
Author(s):  
Dominique E. Martin ◽  
Blake L. Torrance ◽  
Laura Haynes ◽  
Jenna M. Bartley
Keyword(s):  
T Cell Activation ◽  
Cell Activation ◽  
Cell Function ◽  
Immune Cell ◽  
Cell Metabolism ◽  
Cell Types ◽  
Cellular Level ◽  
Lessons Learned ◽  
Immune System Dysfunction ◽  
Different Cell Types

It is well known that aging is associated with dysregulated metabolism. This is seen both in terms of systemic metabolism, as well as at the cellular level with clear mitochondrial dysfunction. More recently, the importance of cellular metabolism in immune cells, or immunometabolism, has been highlighted as a major modifier of immune cell function. Indeed, T cell activation, differentiation, and effector function partly depend on alterations in metabolic pathways with different cell types and functionality favoring either glycolysis or oxidative phosphorylation. While immune system dysfunction with aging is well described, what remains less elucidated is how the integral networks that control immune cell metabolism are specifically affected by age. In recent years, this significant gap has been identified and work has begun to investigate the various ways immunometabolism could be impacted by both chronological age and age-associated symptoms, such as the systemic accumulation of senescent cells. Here, in this mini-review, we will examine immunometabolism with a focus on T cells, aging, and interventions, such as mTOR modulators and senolytics. This review also covers a timely perspective on how immunometabolism may be an ideal target for immunomodulation with aging.

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