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A comparative study of adaptive molecular evolution in different HIV clades Marc Choisy CEPM UMR CNRS-IRD 9926 Montpellier, France
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HIV-2 HIV-1
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HIV-2 HIV-1 M HIV-1 N HIV-1 O
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Adaptive evolution ?
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Purifying selection Adaptive evolution Darwinian evolution (mutation + selection) Neutral evolution (mutation alone)
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No selection Selection AAATGGCAT LysTrpThr dSdS LysTrpThr AATGGCATG dNdN AsnTrpThr AATGGCATC Molecular evolution d N /d S >1 d N /d S <1 d N /d S =1
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envelop proteins env Lipid membrane gp41 gp120 Capsid gag RNA 0 10000 pol enzymes 1 HIV-2 A HIV-1 M A HIV-1 M B HIV-1 M C d N /d S 0 HIV-2 A HIV-1 M A HIV-1 M B HIV-1 M C
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w = d N /d S
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w = d N /d S = p 0 *w 0 + p 1 *w 1 + p 2 *w 2 + p 3 *w 3 w3w3 w2w2 w1w1 w0w0 p1p1 p2p2 p0p0 p3p3 w = d N /d S = p 0 *w 0 + p 1 *w 1 + p 2 *w 2 LRT
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w = d N /d S = p 0 *w 0 + p 1 *w 1 + p 2 *w 2
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Prior probabilities : p 0, p 1, and p 2 Posterior probabilities : f 0 i, f 1 i, and f 2 i w i = d N /d S i = f 0 i *w 0 + f 1 i *w 1 + f 2 i *w 2 5’ 3’ 2 95% 1
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HIV-1 M A HIV-1 M B HIV-1 M D HIV-1 M C HIV-1 O HIV-2 A 95% 2 1 w i = f 0 i *w 0 + f 1 i *w 1 + f 2 i *w 2
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95% 1
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2 w i = f 0 i *w 0 + f 1 i *w 1 + f 2 i *w 2
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Test 1 : H0 : no match between +vely selected sites H1 : match between +vely selected sites Positively selected sites tend to occur at the same position in different clades, except for HIV-2
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Test 2 : H0 : random repartition of +vely selected sites with respect to epitopes H1 : no match between +vely selected sites and epitopes H2 : match between +vely selected sites and epitopes Positively selected sites do not tend to be related to epitopic sites H1 vs H0 H2 vs H0
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Test 3 : H0 : no match between +vely selected sites and glycosylation sites H1 : match between +vely selected sites and glycosylation sites Positively selected sites tend to occur on N-glycosylation sites
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Test 4 : H0 : +vely selected sites have the same strength H1 : +vely selected sites do not have the same strength Not that much difference between clades
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CONCLUSIONS Positively selected sites tend to occur at the same position in different clades, except for HIV-2 Positively selected sites do not tend to be related to epitopic sites Positively selected sites tend to occur on N-glycosylation sites Similar intensity of selection across clades
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CONCLUSIONS Positively selected sites tend to occur at the same position in different clades, except for HIV-2 Positively selected sites do not tend to be related to epitopic sites Positively selected sites tend to occur on N-glycosylation sites Similar intensity of selection across clades Moderates conclusions from Gaschen et al 2002
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CONCLUSIONS Positively selected sites tend to occur at the same position in different clades, except for HIV-2 Positively selected sites do not tend to be related to epitopic sites Positively selected sites tend to occur on N-glycosylation sites Similar intensity of selection across clades Confirms the glycan shield model of Kwong et al. 2002
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Glycan shield model (Kwong et al. 2002)
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Contributors: C. H. Woelk, University of California San Diego, USA. D. L. Robertson, University of Manchester, UK. J. F. Guégan, CEPM, UMR CNRS-IRD 9926, Montpellier, France. Data: Kuiken, C., et al. (2000). HIV Sequence Compendium. Los Alamos, NM, USA: Theoretical Biology and Biophysics Group, Los Alamos National Laboratory. Korber, B., et al. (2000). HIV Molecular Immunology. Los Alamos, NM, USA: Theoretical Biology and Biophysics Group, Los Alamos National Laboratory. Programs: Yang, Z. H. (1997). PAML: a program package for the phylogenetic analysis by maximum likelihood. Computer Applications in the Biosciences 13, 555-556. Hansen, J. E., et al. (1998) NetOglyc: prediction of mucin type O-glycosylation sites based on sequence context and surface accessibility. Glycoconjugate Journal 15, 115-130. ACKNOWLEDGEMENTS
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PAUP* ML on model of codon substitution d N /d S = w 0 p 0 + w 1 p 1 + w 2 p 2
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