Biology subjects

Fadhlaoui, K.

Publications and source records attributed to Fadhlaoui, K..

2 recordsLinked to original sources

bioRxiv2024

Sporadic distribution of a new archaeal genetic code with all TAG codons as pyrrolysine

Numerous genetic codes developed during the evolution of Eukaryotes and three are known in Bacteria, yet no alternative genetic code has been established for Archaea. Some bacterial and archaeal proteins include selenocysteine or pyrrolysine, the 21st and 22nd amino acids, but no evidence establishes the adoption of a genetic code in which a stop codon universally encodes either amino acid. Here, we used proteomics to confirm the prediction that certain Archaea consistently incorporate pyrrolysine at TAG codons, supporting a new archaeal genetic code which we designate Genetic Code 34. This genetic code has 62 sense codons encoding 21 amino acids, and only two stop codons. In contrast with monophyletic genetic code distributions in bacteria, Code 34 occurs sporadically. This, combined with evidence for lateral gene transfer of the code change machinery and anticipated barriers to code reversal, suggests Code 34 arose independently in multiple lineages. TAG codon distribution patterns in Code 34 genomes imply a wide range in time since code switch. We identified many new enzymes containing Pyl residues, raising questions about potential roles of this amino acid in protein structure and function. We used five new PylRS/tRNAPyl pairs from Code 34 archaea to introduce new-to-nature pyrrolysine analogs into proteins in E. coli, demonstrating their utility for genetic code expansion. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=157 SRC="FIGDIR/small/615893v1_ufig1.gif" ALT="Figure 1"> View larger version (42K): org.highwire.dtl.DTLVardef@f363a5org.highwire.dtl.DTLVardef@112f061org.highwire.dtl.DTLVardef@63ad59org.highwire.dtl.DTLVardef@9eddb_HPS_FORMAT_FIGEXP M_FIG C_FIG

genomics↗

bioRxiv2021

Growth temperature is the principal driver of chromatinization in archaea

Across the tree of life, DNA in living cells is associated with proteins that coat chromosomes, constrain their structure and influence DNA-templated processes such as transcription and replication. In bacteria and eukaryotes, HU and histones, respectively, are the principal constituents of chromatin, with few exceptions. Archaea, in contrast, have more diverse repertoires of nucleoid-associated proteins (NAPs). The evolutionary and ecological drivers behind this diversity are poorly understood. Here, we combine a systematic phylogenomic survey of known and predicted NAPs with quantitative protein abundance data to shed light on the forces governing the evolution of archaeal chromatin. Our survey highlights the Diaforarchaea as a hotbed of NAP innovation and turnover. Loss of histones and Alba in the ancestor of this clade was followed by multiple lineage-specific horizontal acquisitions of DNA-binding proteins from other prokaryotes. Intriguingly, we find that one family of Diaforarchaea, the Methanomethylophilaceae, lacks any known NAPs. Comparative analysis of quantitative proteomics data across a panel of 19 archaea revealed that investment in NAP production varies over two orders of magnitude, from <0.02% to >5% of total protein. Integrating genomic and ecological data, we demonstrate that growth temperature is an excellent predictor of relative NAP investment across archaea. Our results suggest that high levels of chromatinization have evolved as a mechanism to prevent uncontrolled helix opening and runaway denaturation - rather than, for example, to globally orchestrate gene expression - with implications for the origin of chromatin in both archaea and eukaryotes.

evolutionary biology↗