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Biomedical subjects

Danith H Ly

Publications and source records attributed to Danith H Ly.

6 recordsLinked to original sources
PubMed2006

Cell-permeable peptide nucleic acid designed to bind to the 5'-untranslated region of E-cadherin transcript induces potent and sequence-specific antisense effects.

Establishing a general and effective method for regulating gene expression in mammalian systems is important for many aspects of biological and biomedical research. Herein we report the antisense activities of a cell-permeable, guanidine-based peptide nucleic acid (PNA) called GPNA. We show that a GPNA oligomer designed to bind to the transcriptional start-site of human E-cadherin gene induces potent and sequence-specific antisense effects and is less toxic to the cells than the corresponding PNA-polyarginine conjugate. GPNA confers its silencing effect by blocking protein translation. The findings reported in this study provide a molecular framework for designing the next generation cell-permeable nucleic acid mimics for regulating gene expression in live cells and intact organisms.

Base Sequence↗
PubMed2006

A simple gamma-backbone modification preorganizes peptide nucleic acid into a helical structure.

Peptide nucleic acid (PNA) is a synthetic analogue of DNA and RNA, developed more than a decade ago in which the naturally occurring sugar phosphate backbone has been replaced by the N-(2-aminoethyl) glycine units. Unlike DNA or RNA in the unhybridized state (single strand) which can adopt a helical structure through base-stacking, although highly flexible, PNA does not have a well-defined conformational folding in solution. Herein, we show that a simple backbone modification at the gamma-position of the N-(2-aminoethyl) glycine unit can transform a randomly folded PNA into a helical structure. Spectroscopic studies showed that helical induction occurs in the C- to N-terminal direction and is sterically driven. This finding has important implication not only on the future design of nucleic acid mimics but also on the design of novel materials, where molecular organization and efficient electronic coupling are desired.

Circular Dichroism↗
PubMed2006

Synthesis of cell-permeable peptide nucleic acids and characterization of their hybridization and uptake properties.

Guanidine-based peptide nucleic acid (GPNA) monomers and oligomers containing all four natural (adenine (A), cytosine (C), guanine (G), and thymine (T)) and two unnatural (2-thiouracil (sU) and 2,6-diaminopurine (D)) nucleobases have been synthesized. Thermal denaturation study showed that GPNA oligomers containing alternate D-backbone configuration bind sequence-specifically to DNA and, when incubated with mammalian cells, localized specifically to the endoplasmic reticulum (ER).

Cell Membrane↗
PubMed2003

Novel binding and efficient cellular uptake of guanidine-based peptide nucleic acids (GPNA).

Incorporation of a guanidine functional group into the PNA backbone facilitates cellular uptake of PNA into mammalian cells with efficiency comparable to that of the TAT transduction domain. The modified PNA recognizes and binds to the complementary DNA strand in accordance with Watson-Crick recognition rules. However, unlike polypyrimidine PNA which binds to DNA in 2:1 stoichiometry, the modified PNA binds to complementary DNA in a 1:1 ratio to form a highly stable duplex.

Circular Dichroism↗
PubMed2003

Embryonic stem cells: a perfect marriage between gene regulation and regenerative medicine.

The mechanism of mammalian gene regulation is highly complex, involving multiple layers of feedback control loops and dynamic chromatin remodeling. The current approach used to dissect the genetic circuitry of mammalian gene regulation utilizes somatic cells and protein fusion as a means to modulate protein interactions. This approach has several limitations that include (i) genome inaccessibility, (ii) high background interferences and, (iii) limited cellular phenotypes. Previously, the two broad fields of research "control of gene expression" and "stem cell biology" had been pursued separately by cell biologists; this review outlines evidence suggesting that integration of these two fields would provide a comprehensive platform for interdisciplinary research seeking to address mechanistic questions concerning gene regulation-that could have enormous implication for the development of therapeutic applications.

Animals↗