1: EMBO J. 1998 Mar 2;17(5):1434-45. 

The novel homeoprotein Prep1 modulates Pbx-Hox protein cooperativity.

Berthelsen J, Zappavigna V, Ferretti E, Mavilio F, Blasi F.

Dipartimento di Genetica e Biologia dei Microrganismi dell'Universita, H.S.
Raffaele, via Olgettina 58, 20132, Milan, Italy.

The products of the mammalian Pbx and Drosophila exd genes are able to interact
with Hox proteins specifically and to increase their DNA binding affinity and
selectivity. In the accompanying paper we show that Pbx proteins exist as stable
heterodimers with a novel homeodomain protein, Prep1. Here we show that
Prep1-Pbx interaction presents novel structural features: it is independent of
DNA binding and of the integrity of their respective homeodomains, and requires
sequences in the N-terminal portions of both proteins. The Prep1-Pbx
protein-protein interaction is essential for DNA-binding activity. Prep1-Pbx
complexes are present in early mouse embryos at a time when Pbx is also
interacting with Hox proteins. The use of different interaction surfaces could
allow Pbx to interact with Prep1 and Hox proteins simultaneously. Indeed, we
observe the formation of a ternary Prep1-Pbx1-HOXB1 complex on a
HOXB1-responsive target in vitro. Interaction with Prep1 enhances the ability of
the HOXB1-Pbx1 complex to activate transcription in a cooperative fashion from
the same target. Our data suggest that Prep1 is an additional component in the
transcriptional regulation by Hox proteins.

PMID: 9482740 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


2: EMBO J. 1998 Mar 2;17(5):1423-33. 

Prep1, a novel functional partner of Pbx proteins.

Berthelsen J, Zappavigna V, Mavilio F, Blasi F.

Dipartimento di Genetica e Biologia dei Microrganismi dell'Universita, DIBIT,
H.S. Raffaele, via Olgettina 58, 20132, Milan, Italy.

The human transcription factor, UEF3, is important in regulating the activity of
the urokinase plasminogen activator (uPA) gene enhancer. The UEF3 DNA target
site is a regulatory element in the promoters of several growth factor and
protease genes. We reported previously that purified UEF3 is a complex of
several subunits. In this paper we report the cloning of the cDNA of one of the
subunits which encodes for a novel human homeodomain protein, which we have
termed Prep1. The Prep1 homeodomain belongs to the TALE class of homeodomains,
is most closely related to those of the TGIF and Meis1 proteins, and like these,
recognizes a TGACAG motif. We further identify the other UEF3 subunit as a
member of the Pbx protein family. Unlike other proteins known to interact with
Pbx, Prep1 forms a stable complex with Pbx independent of DNA binding.
Heterodimerization of Prep1 and Pbx results in a strong DNA binding affinity
towards the TGACAG target site of the uPA promoter. Overall, these data indicate
that Prep1 is a stable intracellular partner of Pbx in vivo.

PMID: 9482739 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------


3: Genomics. 1998 Jan 15;47(2):323-4. 

PKNOX1, a gene encoding PREP1, a new regulator of Pbx activity, maps on human
chromosome 21q22.3 and murine chromosome 17B/C.

Berthelsen J, Viggiano L, Schulz H, Ferretti E, Consalez GG, Rocchi M, Blasi F.

Unit of Molecular Genetics, H.S. Raffaele, Milan, Italy.

PMID: 9479508 [PubMed - indexed for MEDLINE]


---------------------------------------------------------------