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J. Virol., 06 1996, 3449-3460, Vol 70, No. 6
P Lutz, F Puvion-Dutilleul, Y Lutz and C Kedinger
Sequence elements (DE) located downstream of the adenovirus major late
promoter start site have previously been shown to be essential for the
activation of this promoter after the onset of viral DNA replication. Two
proteins (DEF-A and DEF-B) bind to these elements in a late-phase-
dependent manner and contribute to this activation. DEF-B corresponds to a
dimer of the adenovirus IVa2 gene product (pIVa2, 449 residues), while
DEF-A is a heteromeric protein also comprising pIVa2. As revealed by
specific immunofluorescence staining of infected cells, pIVa2 is targeted
to the nucleus, where it distributes to both nucleoplasmic and nucleolar
structures. We have identified the pIVa2 nuclear localization signal (NLS)
as a basic peptide element at the C terminus of the protein (residues 432
to 449). An element essential for nucleolar localization (NuLS) has been
mapped in the N-terminal part of pIVa2 (between residues 50 and 136). While
NuLS activity is dependent upon an intact NLS, we show that both NLS and
NuLS functions are independent of specific DNA-binding activity. As
visualized by immunoelectron microscopy, pIVa2 is detected in the
nucleoplasm at the level of the fibrillogranular network which is active in
viral transcription. More surprisingly, pIVa2 accumulates within
electron-dense amorphous inclusions found both in the nucleoplasm and in
the nucleolus. Altogether, these results suggest that, besides controlling
major late promoter transcription, pIVa2 serves additional, as yet unknown
functions.
Copyright © 1996, American Society for Microbiology
Nucleoplasmic and nucleolar distribution of the adenovirus IVa2 gene product
Institut de Genetique et de Biologie Moleculaire et Cellulaire, Universite Louis Pasteur, C.U.de Strasbourg, France.
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