Biology subjects

Olivier Rivoire

Publications and source records attributed to Olivier Rivoire.

3 recordsLinked to original sources

bioRxiv2015

Diversity of immune strategies explained by adaptation to pathogen statistics

Biological organisms have evolved a wide range of immune mechanisms to defend themselves against pathogens. Beyond molecular details, these mechanisms differ in how protection is acquired, processed and passed on to subsequent generations - differences that may be essential to long-term survival. Here, we introduce a mathematical framework to compare the long-term adaptation of populations as a function of the pathogen dynamics that they experience and of the immune strategy that they adopt. We find that the two key determinants of an optimal immune strategy are the frequency and the characteristic timescale of the pathogens. Depending on these two parameters, our framework identifies distinct modes of immunity, including adaptive, innate, bet-hedging and CRISPR-like immunities, which recapitulate the diversity of natural immune systems.

Evolutionary Biology↗

bioRxiv2015

Evolution-Based Functional Decomposition of Proteins

The essential biological properties of proteins - folding, biochemical activities, and the capacity to adapt - arise from the global pattern of interactions between amino acid residues. The statistical coupling analysis (SCA) is an approach to defining this pattern that involves the study of amino acid coevolution in an ensemble of sequences comprising a protein family. This approach indicates a functional architecture within proteins in which the basic units are coupled networks of amino acids termed sectors. This evolution-based decomposition has potential for new understandings of the structural basis for protein function, but requires broad further testing by the scientific community. To facilitate this, we present here the principles and practice of the SCA and introduce new methods for sector analysis in a python-based software package. We show that the pattern of amino acid interactions within sectors is linked to the divergence of functional lineages in a multiple sequence alignment - a model for how sector properties might be differentially tuned in members of a protein family. This work provides new tools for understanding the structural basis for protein function and for generally testing the concept of sectors as the principal functional units of proteins.

Biochemistry↗

bioRxiv2014

Conserved units of co-expression in bacterial genomes: an evolutionary insight into gene regulation

Genome-wide measurements of transcriptional activity in bacteria indicate that the transcription of successive genes is strongly correlated beyond the scale of operons. However, the underlying mechanisms are poorly characterized and a systematic method for identifying local groups of co-transcribed genes is lacking. Here, we identify supra-operonic segments of consecutive genes by comparing gene proximity in thousands of bacterial genomes. Structurally, the segments are contained within micro-domains delineated by known nucleoid-associated proteins, and they contain operons with specific relative orientations. Functionally, the operons within a same segment are highly co-transcribed, even in the absence of regulatory factors at their promoter regions. Hence, operons with no common regulatory factor can be co-regulated if they share a regulatory factor at the level of segments. To rationalize these findings, we put forward the hypothesis supported by RNA-seq data that facilitated co-transcription, the feedback of transcription into itself involving only DNA and RNA-polymerases, may represent both an evolutionary primitive and a functionally primary mode of gene regulation.

Systems Biology↗