GSBS Student Publications


RNAi in human cells: basic structural and functional features of small interfering RNA

GSBS Program

Biochemistry & Molecular Pharmacology

UMMS Affiliation

Graduate School of Biomedical Sciences; Department of Biochemistry and Molecular Pharmacology



Document Type


Medical Subject Headings

Animals; Cross-Linking Reagents; Ficusin; Fluorescent Dyes; Genes, Reporter; Green Fluorescent Proteins; Hela Cells; Humans; Luminescent Proteins; Microscopy, Fluorescence; Molecular Structure; *Nucleic Acid Conformation; Photosensitizing Agents; RNA Interference; RNA Replicase; RNA, Small Interfering


Life Sciences | Medicine and Health Sciences


We investigated the mechanism of RNA interference (RNAi) in human cells. Here we demonstrate that the status of the 5' hydroxyl terminus of the antisense strand of a siRNA determines RNAi activity, while a 3' terminus block is tolerated in vivo. 5' hydroxyl termini of antisense strands isolated from human cells were phosphorylated, and 3' end biotin groups were not efficiently removed. We found no requirement for a perfect A-form helix in siRNA for interference effects, but an A-form structure was required for antisense-target RNA duplexes. Strikingly, crosslinking of the siRNA duplex by psoralen did not completely block RNA interference, indicating that complete unwinding of the siRNA helix is not necessary for RNAi activity in vivo. These results suggest that RNA amplification by RNA-dependent RNA polymerase is not essential for RNAi in human cells.

Rights and Permissions

Citation: Mol Cell. 2002 Sep;10(3):549-61.

Related Resources

Link to article in PubMed

Journal Title

Molecular cell

PubMed ID