Stochastic gene expression in a lentiviral positive-feedback loop: HIV-1 Tat fluctuations drive phenotypic diversity.
HIV-1 Tat transactivation is vital for completion of the viral life cycle and has been implicated in determining proviral latency. We present an extensive experimental/computational study of an HIV-1 model vector (LTR-GFP-IRES-Tat) and show that stochastic fluctuations in Tat influence the viral latency decision. Low GFP/Tat expression was found to generate bifurcating phenotypes with clonal populations derived from single proviral integrations simultaneously exhibiting very high and near zero GFP expression. Although phenotypic bifurcation (PheB) was correlated with distinct genomic integration patterns, neither these patterns nor other extrinsic cellular factors (cell cycle/size, aneuploidy, chromatin silencing, etc.) explained PheB. Stochastic computational modeling successfully accounted for PheB and correctly predicted the dynamics of a Tat mutant that were subsequently confirmed by experiment. Thus, Tat stochastics appear sufficient to generate PheB (and potentially proviral latency), illustrating the importance of stochastic fluctuations in gene expression in a mammalian system.
Weinberger
Leor S
LS
Biophysics Graduate Group, The Howard Hughes Medical Institute, University of California, Berkeley, California 94720, USA. leor@princeton.edu
Burnett
John C
JC
Toettcher
Jared E
JE
Arkin
Adam P
AP
Schaffer
David V
DV
D044822:Biodiversity; D003198:Computer Simulation; D025461:Feedback, Physiological; D015967:Gene Expression Regulation, Viral; D015756:Genes, tat; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D019169:Jurkat Cells; D008954:Models, Biological; D013269:Stochastic Processes; D015533:Transcriptional Activation; D016662:Virus Integration; D014779:Virus Replication
D049452:Green Fluorescent Proteins