The progene hypothesis: the nucleoprotein world and how life began

Abstract

In this article, I review the results of studies on the origin of life distinct from the popular RNA world hypothesis. The alternate scenario postulates the origin of the first bimolecular genetic system (a polynucleotide gene and a polypeptide processive polymerase) with simultaneous replication and translation and includes the following key features:The bimolecular genetic system emerges not from mononucleotides and monoamino acids, but from progenes, namely, trinucleotides aminoacylated on 3′–end by a non-random amino acid (NpNpNp ~ pX ~ Aa, where N—deoxyribo- or ribonucleoside, p—phosphate, X—a bifunctional agent, for example ribose, Aa—amino acid, ~ macroerge bond). Progenes are used as substrates for simultaneous synthesis of a polynucleotide and a polypeptide. Growth of the system is controlled by the growing polypeptide, and the bimolecular genetic system emerges as an extremely rare event. The first living being (virus-like organism protoviroid, Protoviroidum primum) arises and reproduces in prebiotic liposome-like structures using progenes. A population of protoviroids possessing the genetic system evolves in accordance with the Darwinian principle. Early evolution from protoviroid world to protocell world is shortly described.The progene forming mechanism (NpNp + Np ~ pX ~ Aa) makes it possible to explain the emergence of the prebiotic physicochemical group genetic code, as well as the selection of organic compounds for the future genetic system from the racemic environment.The protoviroid is reproduced on a progene basis via replicative transcription-translation (RTT, the first molecular genetic process) that is similar to its modern counterparts. Nothing is required for the emergence and reproduction of the protoviroid except for progenes and conditions for their formation.The general scheme of early evolution is as follows: prebiotic world → protoviroid (nucleoprotein) world → protocell (DNA-RNA-protein) world → LUCA (Last Universal Common Ancestor) → modern cell world. This scheme exclude the existence of an independent RNA world as predecessor of the cellular world.ReviewersDr. Thomas Dandekar, Dr. Bojan Zagrovic and Dr. Anthony Poole

Origin of Biological Nucleic Acids and the First Genetic System (The Progene Hypothesis)

“…It is the progene hypothesis [9,10] that considered long prebiotic polynucleotides and polypeptides are synthesized not from mononucleotides and monoamino acids. First nucleotides and amino acids are united into special structures called progenes, and then a polynucleotide and a polypeptide are synthesized from progenes.…”

“…2) The first processive polymerase is a protein (nucleoprotein world hypothesis) [5][6][7][8][9][10].…”

Does the discovery of the mimivirus call into question attempts to define life?

“…Many advances in science have come from challenging past conventional wisdom and this approach may not represent competing viewpoints in fast moving fields (Popa, 2012). There are still competing hypotheses for the origin of life (Altstein, 2015) and so this approach could not represent all viewpoints, only the hypothesis that received the most attention in the literature (Popa, 2012).…”

Homochirality of Organic Matter – Objective Law or Curious Incident?

“…Keywords: amino acids · chiral pool · origin of life · primary particles · meteorite impact played the most important rolei nt he emergence of living systems.T he idea of as imultaneousg rowth of polynucleotide and polypeptide chains by condensationo fs imple "progenes" appearsv ery interesting. [20] At the present time,i ti sd ifficult to showp reference to one of the three main polymeric components of living matter -p roteins,R NA,o rc arbohydratep olymers -i n the capacity of the leading one in the early stage of prebiotic evolution, but all of them have in common them ost important uncertainty withr espectt ot he selection of Lamino acid or D-carbohydrate blocks for the formation of polymerc hains.I ng eneral, the origin of biological homochirality remains the key problem in the emergence of the very first self-replicatingp olymeric systems.I ndeed, in our three-dimensional world, only well-designedt hreedimensionala ctive macromolecules can functiona se nantiospecific catalysts in the faultless replication of nucleic acids and in the synthesis and action of life-determining proteins.O bviously,h omochirality of all building elements is the important condition for both life emergence and life sustenance.I na ny case,f or life to start on Earth or elsewhere,itiscritical that amino acids,sugars,and nucleosidesb ep resent in the predominanth omochiral form. [21][22][23] Thea bove homochirality requiremento ft he initial pool of building blocks for the enantioselective self-assembling of the first self-replicating polymeric system follows from simple statistical estimations.…”

“…If 20 different protein aminoa cids were to statistically form ar elatively short polypeptide incorporating 50 building units (molecular mass of ca. 4k Da), the number of possible chain structures would amount to 20 50 !W hile taking into account the principal racemic nature of each amino acid, the above number mustb ea dditionally multiplied by af actor of 2 20 .B yno means,c ould nature provider esources for exploringa ll the possibilities!O bviously,t he starting amino-acid pool has to be enriched in L-enantiomers. Only under this condition,c ould the happy amino-acid sequencei nahomochiral polypeptide,w hich allowed its further enantioselective self-replication, occasionally form rather early.F rom this view point, one cannot exclude the scenario of life originatingf rom one single molecule.…”