download report - Istituto Pasteur

P a r t i c i p a n t s :
Elisa Caffarelli, Alessandro Fatica, Carlo Presutti,
researchers; Michela Denti, Fernanda De Angelis,
Mariangela Morlando, post-doc fellows; Monica Ballarino,
Pietro Laneve, Alessandro Rosa, PhD students.
C o l l a b o r a t i o n s :
Dipartimento di Medicina sperimentale, Sapienza-Università di
Roma (Prof. Alberto Gulino); Dipartimento di Istologia ed
Embriologia Medica, Sapienza-Università di Roma (Prof. Antonio
Musarò); TIGEM, Napoli (Prof. Alberto Auricchio); City of
Hope, Duarte, USA (Prof. John Rossi).
Report of activity
The aim of this project was to exploit and further
develop the high potential of RNA-based methodologies
for the comprehension of the molecular basis of
several processes of gene regulation and to apply this
knowledge to the study and cure of several genetic
disorders, such as cancer or inherited diseases.
The project covers topics ranging from the biosynthesis
of small-non coding RNAs to the study of their
functions in cell growth, differentiation and diseases.
In a parallel line of research, we intend to exploit
the vast potential of different RNA activities (antisense
and interference) for human therapy, based on
an advanced understanding of the underlying
mechanisms.
To achieve these goals, integrated and multidisciplinary
action was required including basic research
and development, genetic approaches, as well as cell
biology assessment.
The miRNA “factory”
miRNA are generated from a longer RNA polymerase
II derived transcript by a stepwise process involving
two RNaseIII enzymes: Drosha acting on nuclear primiRNA
and then Dicer cleaving pre-miRNAs in the
cytoplasm. We demonstrated that, in human HeLa
Principal investigator: Irene Bozzoni
Professor of Molecular Biology
Dipartimento di Genetica e Biologia Molecolare
Tel: (+39) 06 49912202; Fax: (+39) 06 49912500
irene.bozzoni@uniroma1.it
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Molecular genetics of eukaryotes - AREA 3
RNA-RNA and RNA-protein interactions in the cell nucleus:
structure, function and biosynthesis of a novel class
of small non-coding RNAs
cells, Drosha processing, as the major RNA-processing
activities acting on pre-mRNAs, occurs during
transcription on both dedicated and intronic miRNA
genes. In this latter case we showed that the two 5'-3'
and 3'-5' RNA exonucleases activities colocalized
with the Microprocessor complex on chromatin
associated with intronic miRNA genes. We also
demonstrated that Drosha cleavage occurs before the
host intron is spliced out and that co-transcriptional
pre-miRNA processing does not affect the accumulation
of the host spliced mRNA. These results allowed
us to predict that both mature miRNAs and mRNAs
derive from a common nascent transcript.
Mammalian intronic-miRNAs are transcriptionally
linked to the expression of their host genes. As the
expression of miRNA-dedicated genes is dependent
from their own promoter we are investigating
whether specific miRNA cis-acting signals are
required for the control of their biosynthesis.
Role of miRNAs in hematopoietic
differentiation
In consideration of the important role played by
miRNA in hematopoiesis and leukaemia, we have
proceeded to the identification and characterisation
of miRNAs with potential role in myeloid differentiation
(reviewed in Fatica et al., Biochem Soc Trans.
2008, 36:1201-5).
In the direction of studying the molecular circuitries
regulated by miRNAs and involved in the control of
specific differentiation lineages, we have identified a
new pathway by which the master hematopoietic
transcription factor PU.1 regulates human monocytic
differentiation. This includes the lineage–specific
miR-424 and the transcriptional factor NFI-A. We
have shown that PU.1 and these two components are
linked to each other in a finely tuned temporal and
regulatory circuitry: PU.1 activates the transcription
of miR-424 and this up-regulation appears to be
involved in stimulating monocyte differentiation
through miR-424 dependent translational repression