The odd couple: A repressor protein and a retroelement RNA.
We
described a novel mechanism for reversible regulation of gene
transcription involving PSF, a conserved mammalian tumor-suppressor
protein, and mVL30 RNA, a mouse noncoding retroelement RNA (1-4). PSF
contains a DNA-binding domain (DBD) that binds to certain genes and
represses transcription, and also contains RNA-binding domains (RBD)
that bind mVL30 RNA, forming a complex that releases PSF from a gene
and reverses repression. This regulatory mechanism has a role in
oncogenesis and steroidogenesis, and probably in regulating cell
proliferation during development. We isolated human retroelement RNAs
that have a similar function as mVL30 RNA, which is not present in
human cells. PSF belongs to a family of putative tumor-suppressor
proteins containing RBD and DBD, and we are testing whether other
members of this family have a similar function as PSF in regulating
gene transcription. Other experiments include a molecular analysis of
the protein-RNA regulatory mechanism and its normal and pathological
roles.
Targeting pathological blood vessels for immunotherapy of cancer and macular degeneration.
We
constructed a molecule called an Icon that activates a cytolytic immune
response against cells expressing the transmembrane receptor tissue
factor (TF). TF is expressed on endothelial cells lining the luminal
surface of pathological blood vessels in tumors. The model for the Icon
molecule is a Camelid IgG1 antibody composed of two heavy chains
without associated light chains, each chain containing a VH targeting
domain conjugated to the Fc effector domain. The Icon is similarly
composed of two chains, each chain containing fVII, the natural ligand
for TF as the targeting domain conjugated to an Fc domain. The Icon
binds to TF with stronger affinity and specificity than can be achieved
with an anti-TF antibody. Because the Icon is synthesized by
recombinant DNA technology, the fVII and Fc domains can be derived from
the species of choice. Pre-clinical immunotherapy tests were done by
encoding the Icon in an adenoviral vector, which was injected into a
tumor in a mouse model of human metastatic cancer (1-3). The infected
tumor cells synthesized and secreted the icon into the systemic
circulation, and the blood-borne Icon molecules bound to TF, activating
an immune response that destroyed the pathological blood vessels
without harming normal vessels. A clinical trial of the protocol is
being arranged for cancer patients. Similar results were obtained with
a mouse model of macular degeneration (4). We are testing a
nanoparticle vector as an alternative to an adenoviral vector for
delivering the Icon gene