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\dateposted{2023-12-19}
\datepublished{2024-03-29}
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%\makeatletter
%\def\TITREspecial{\relax}
%\def\cdr@specialtitle@english{A tribute to Fran\c{c}ois Gros, a founding father of molecular biology}
%%\def\cdr@specialtitle@french{Un hommage \`a Fran\c{c}ois Gros, un des p\`eres de la biologie mol\'eculaire}
%\makeatother


\title{Fran\c{c}ois Gros: from antibiotics to messenger RNA}

\alttitle{Fran\c{c}ois Gros : des antibiotiques aux ARN messagers}

\author{\firstname{Moshe} \lastname{Yaniv}\CDRorcid{0000-0001-7900-6322}}
\address{Department of Developmental and Stem Cell
Biology, Institut Pasteur, 28 rue du Docteur Roux, 75724 Paris cedex 
15, France}
\email{moshe.yaniv@pasteur.fr}

\keywords{\kwd{Fran\c{c}ois Gros}
\kwd{messenger RNA}
\kwd{translation}
\kwd{myogenesis}}

\altkeywords{\kwd{Fran\c{c}ois Gros}
\kwd{ARN messager}
\kwd{traduction}
\kwd{myogen\`{e}se}}

\begin{abstract} 
Fran\c{c}ois Gros was a prominent French Molecular Biologist who made a
major contribution to the discovery of messenger RNA in 1961. He
pursued outstanding research on bacterial mRNA and its translation into
proteins followed by pioneering work on muscle differentiation. I was
lucky to be among his graduate students and owe much of my success in
science to him. In this short text I will describe how the initial
post-war studies of Fran\c{c}ois guided him to discover the existence
of short-lived RNA in bacteria, the messenger RNA containing the
information for protein synthesis. I will also recount the influence he
had on his students and their carrier in science.\vspace*{2pt}
\end{abstract}

\begin{altabstract} 
Fran\c{c}ois Gros \'{e}tait un \'{e}minent biologiste mol\'{e}culaire
fran\c{c}ais qui a contribu\'{e} de mani\`{e}re d\'{e}cisive \`{a} la
d\'{e}couverte de l'ARN messager en 1961. Il a poursuivi des recherches
remarquables sur l'ARNm bact\'{e}rien et sa traduction en
prot\'{e}ines, suivies de travaux pionniers sur la diff\'{e}renciation
musculaire. J'ai eu la chance d'\^{e}tre l'un de ses \'{e}tudiants de
th\`{e}se d'\'{E}tat et je lui dois une grande partie de ma
r\'{e}ussite scientifique. Dans ce court texte, je d\'{e}crirai comment
les \'{e}tudes initiales d'apr\`{e}s-guerre de Fran\c{c}ois l'ont
amen\'{e} \`{a} d\'{e}couvrir l'existence d'un ARN \`{a} courte
dur\'{e}e de vie dans les bact\'{e}ries, l'ARN messager, qui contient
l'information n\'{e}cessaire \`{a} la synth\`{e}se des prot\'{e}ines.
Je raconterai \'{e}galement l'influence qu'il a eue sur ses
\'{e}tudiants et leur carri\`{e}re scientifique.
\end{altabstract}

\maketitle

\vspace*{4pt}

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\section{Introduction}\label{sec1}

I was extremely lucky and honoured to be accepted as a PhD student by
Fran\c{c}ois 59 years ago. He took the risk to accept a chemistry
graduate from Israel with very little background in molecular biology
or genetics. The laboratory was located in the Institut de
Biologie-Physico Chimie (IBPC) in the Latin Quarter, spread over five
floors, very crowded, very international with wonderful science and
sense of camaraderie. We had close contact with the laboratories of
Monod and Jacob and used to go over to the Institut Pasteur almost
twice a week for seminars.

Fran\c{c}ois already had many responsibilities at the national level
and his office was open for visitors looking for advice and help from
around France and beyond. Still he insisted on doing experiments
himself, labelling phage T4 infected cells in the cellar and being
interrupted by Genevieve, his loyal secretary, who called him to
respond to an urgent phone call. In the meantime, the infected bacteria
would lyse and the experiment had to be repeated.

I was lucky to meet my future wife in the laboratory, Josette
Rouvi\`{e}re, and we shared long days and evenings working hard in the
laboratory. The Latin Quarter had an advantage, we could go to see a
movie while the ultracentrifuge was running for two hours to isolate
ribosomes or other subcellular fractions.

The Institute was close to the barricades erected by the students in
May 1968; we were in the laboratory when the CRS charged the barricades
and we opened the door of the Institute to let in young students
escaping the police as well as photographers who used our dark room to
develop their films and print some pictures. When we called
Fran\c{c}ois, he strongly approved our action. Later, Jacques Monod
came to help protect the students seeking refuge at the Institute.

Early on during my PhD, Fran\c{c}ois was always available for
discussions, encouraged my initiatives and introduced me to the
international scientific community. He succeeded in defending my
candidature for a CNRS position that I received during my second year
of graduate work, an unattainable dream for current day students.
Fran\c{c}ois sent me to participate in prestigious scientific meetings
and helped me secure short term EMBO fellowships to travel to Fred
Sanger's laboratory in Cambridge UK, to sequence two of the first
tRNA species.

Since that time, Fran\c{c}ois was my guide and inspiration in science.

Later when we came back from our postdoctoral training in Stanford, he
gave Josette and me space and support to start our own groups at the
Institut Pasteur where he moved his lab in 1972. This was a launching
pad to becoming an independent head of a unit in the Molecular Biology
Department at the Institut Pasteur.

His support and encouragements never ceased during all the years we
have been together at the Pasteur Institute and at the Academy. A
long-standing friendship developed between Fran\c{c}ois and Daniele and
Josette and me. We miss Fran\c{c}ois.

\section{From antibiotics to mRNA and beyond} 

In this short text, I would like to demonstrate briefly how
Fran\c{c}ois moved from his initial study of the mode of action of
antibiotics to discover mRNA.

Fran\c{c}ois joined the Service de Biochimie, as it was called at the
time, headed by Professor Michel Macheboeuf in the Pasteur Institute in
1945. A subject ``\`{a} la mode'' after the war was the research on the
mode of action of the newly discovered antibiotics and this was the
field in which he embarked at the Pasteur laboratory. I will mention
several of his early publications from this period. Typical for these
early post war years, the publications are in
French~\cite{1,2,3}.

Studying the action of streptomycin, Fran\c{c}ois and others realized
that this antibiotic precipitated nucleic acids in the test tube and
that this could explain its antibacterial action. Quite a prediction,
many years before the observation by X-ray crystallography that it
binds to three RNA helices of the small ribosomal subunit, interferes
with the correct recognition of the incoming aminoacyl tRNA and thus
inhibits the synthesis of the bacterial proteins.

After completion of a PhD and the premature death of M. Macheboeuf,
Fran\c{c}ois joined the laboratory of Jacques Monod for a short period
before leaving for a postdoctoral training in the United States. Quite
an experience with Sol Spiegelman in Urbana, Illinois and Rollin
Hotchkiss at the \mbox{Rockefeller}
\mbox{Institute.} With Spiegelman, he started to
study the effect of nucleic acid analogues on enzymatic adaptation in
yeast.

Coming back to the Institut Pasteur, in the service now directed by
Jacques Monod, Fran\c{c}ois pursued the study of the effect of nucleic
acid analogues on the synthesis of proteins. Together with Alain
Bussard and Shiro Naono, he observed that on the addition of
fluorouracil, an analogue of uracil, the induction of an active enzyme,
beta-galactosidase, is partially inhibited due to the production of an
inactive\break enzyme.

This provided an indication that RNA may be the template for the
synthesis of proteins~\cite{4,5,6}. However, it was still
unclear which RNA. In fact, for a number of years it had been  observed
that the ribosomes are the site of synthesis of proteins in mammalian
cells. One hypothesis postulated that the ribosomal RNA is varying
among the ribosomal particles and that it may be the template for the
biosynthesis of specific proteins.

At the end of the fifties, it remained to establish what is the
template for protein synthesis and to prove the mRNA hypothesis that
emerged during the genetic studies that preceded the conception of the
Operon Theory by Monod and Jacob.

Two distinct experimental approaches were taken. Fran\c{c}ois Gros
travelled to Harvard to join forces with scientists in James Watson's
laboratory to attempt to label \textit{E. coli} cultures with
radioactive phosphate and follow the fate of the label by
ultracentrifugation on sucrose gradients. Fran\c{c}ois Jacob together
with Sydney Brenner travelled to Caltech to use density isotope
labelling to follow the fate of newly synthesized RNA after T4
infection of \textit{E. coli} cells. Both series of experiments
confirmed the existence of rapidly labelled unstable RNA and were
published back to back in Nature in June 1961~\cite{7,8}. At the
same time the Operon paper appeared in the Journal of Molecular
Biology. The discovery of messenger RNA in bacteria was followed by the
generalization of this class of RNA to all living cells~\cite{9}.
Furthermore, it was followed by an intense competition to establish and
decipher the genetic code, the match between the nucleotide triplets in
the mRNA, the codon, and the corresponding amino acid in the protein.

These were certainly the great years of the nascent molecular biology
and Fran\c{c}ois was a major actor in this revolution.

\section{Transcription and mRNA translation}

Following the pioneering studies on mRNA, Fran\c{c}ois was invited to
join the IBPC in the Latin Quarter, where I joined his laboratory in
1964. Fran\c{c}ois began to study the regulation of the synthesis of
specific mRNAs, typically the RNA produced during phage Lambda
development, those of the lactose operon during induction of
beta-galactosidase or during phage T4 
infection~\cite{10,11,12}. At this time, Klaus Scherrer in
Fran\c{c}ois' laboratory started to study the synthesis of globin
mRNA, its precursors and mature RNA in the duck and he will recount
these studies in his contribution.

It was certainly the curiosity of Fran\c{c}ois and the desire to expand
our understanding of living organisms beyond microorganisms that drove
Fran\c{c}ois to initiate studies of RNA synthesis in a model of cell
differentiation in which myoblasts undergo the transition to 
myotubes~\cite{13}. Margaret Buckingham will discuss this period in
Fran\c{c}ois' trajectory that resulted in his laboratory becoming one
of the world leaders in the emerging field of molecular and cell
biology.

The existence of mRNA also raised questions about the mechanisms
involved in protein synthesis. Upon the suggestion of Fran\c{c}ois, I
embarked on the study of \textit{E. coli} temperature sensitive mutants
that were defective in protein synthesis at the non-permissive
temperature.

I could show that the mutations occurred in genes encoding the enzymes
responsible for linking specific amino acids to their cognate tRNA that
recognizes the triplet codons on the mRNA~\cite{14}. I went on to
study the properties of Valyl-tRNA synthetase, the enzyme that links
the specific amino acid to its cognate tRNA. I isolated the
corresponding three Valine tRNAs and established their primary sequence
during several visits to the laboratory of Fred Sanger in Cambridge,
UK. Together with Alain Favre, we introduced an intramolecular
cross-link following UV irradiation of the Valyl-tRNA and together with
Jacques Ninio we built a model that predicted half of the 3D structure
of tRNAs~\cite{15,16} as solved later by X-ray crystallography.

Michel Revel in the laboratory isolated the bacterial protein factors
that are essential for the positioning of the ribosome at the first
codon of the mRNA and for the initiation step of the synthesis of the
\unskip\break protein~\cite{17,18}.

\section{How my science was influenced by Fran\c{c}ois}

I continued to study the world of tRNA with Paul Berg at Stanford where
I demonstrated the role of the anticodon in its recognition by the
cognate aminoacyl synthetase~\cite{19}.

When we came back from Stanford, Josette and I became part of the
service de Biochimie that he directed upon his return to the Pasteur
Institute. With the endorsement of Fran\c{c}ois and his support, I
started to study small DNA tumour viruses, Polyomavirus and SV40, with
a focus on the structure and replication of their genomes and their
transcription in the nucleus. I was certainly influenced by the step
Fran\c{c}ois had taken in studying the muscle system and his great
interest in the structure of chromatin and chromosomal proteins. We
could show that the circular viral DNA is associated with nuclear
histones as minichromosomes, that newly replicated viral DNA is rapidly
assembled into nucleosomes~\cite{20} and that the transcription
control region is free of nucleosomes~\cite{21}. This became a
general mark of transcription control regions in eukaryotes.
Furthermore, we showed in collaboration with Daniel Blangy, that
mutants of Polyomavirus, adapted to grow in embryonic carcinoma cells,
harbour mutations and rearrangements in their enhancer sequences
included in the nucleosome free region~\cite{22,23}. Josette
studied bacterial chromosomal proteins and discovered the HU protein, a
small conserved DNA-binding protein that condenses the bacterial
DNA~\cite{24}. Upon the departure of Fran\c{c}ois Cuzin to Nice, I
became the head of the DNA Tumour Viruses Unit, three floors below in
the building, but kept close contact with Fran\c{c}ois and his floor.

Several years later I moved to another building at the Institut
Pasteur, Fran\c{c}ois was more involved in government work but we still
saw each other frequently and discussed science as usual. Like
Fran\c{c}ois, we became more and more interested in transcription and
cell differentiation, isolating transcription factors that are
essential for Polyomavirus and SV40 transcription or for hepatic cell
differentiation, in collaboration with Mary
Weiss~\cite{25,26,27}. Finally, we came back to chromatin by
studying chromatin remodelling complexes essential for opening the
chromatin during transcription~\cite{28}. Several of the genes
encoding for transcription factors or chromatin remodeler subunits were
identified as\unskip\break oncogenes or tumour suppressor genes bringing us closer
to the study of cancer~\cite{29,30}. Similarly, two of the liver
specific transcription factors were discovered as human disease genes
associated with diabetes and kidney polycystic disease bringing us
closer to human diseases~\cite{31}.
Finally, the arrival at the
Pasteur of our regretted colleague G\'{e}rard Orth, sponsored by
Fran\c{c}ois as the director, opened a long-standing collaboration
between both our laboratories on the study of the genome of the
papilloma group of viruses and on their transcription and replication.

\section{Conclusions}

In conclusion, this short summary of the first part of the path of
Fran\c{c}ois from antibiotics to mRNA and protein synthesis illustrates
the constant desire of Fran\c{c}ois to always move forward and
investigate new biological horizons, which he succeeded in\break doing.

He knew how to instil passion for science, for hard work, curiosity and
dedication in his collaborators. He encouraged our maturation and
development into independent successful scientists, open to the world
around us and motivated to improve human well-being. We are grateful to
Fran\c{c}ois for the chance to be close to him during so many years. I
always admired the enormous knowledge of Fran\c{c}ois, his curiosity
and his incomparable memory. I also envied his unlimited capacity to
conduct top science, while, in parallel, being involved in advancing
science in France and in developing countries, helping friends and
colleagues, with his door always open for advice. I admired his
capacity to find time to write monographs about the advances of
molecular biology and the importance of science for society. He kept
his interest and full knowledge of innovations in science many years
after closing his laboratory, following the entire field of life
sciences.

We miss him.

\section*{Declaration of interests}
The authors do not work for, advise, own shares in, or receive funds
from any organization that could benefit from this article, and have
declared no affiliations other than their research organizations.

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