Human U2 small nuclear RNA genes contain an upstream enhancer

Area of Science:

• Molecular Biology
• Gene Regulation
• Genomics

Background:

• Human U1 and U2 small nuclear RNA (snRNA) genes are highly active RNA polymerase II transcription units.
• These genes lack a canonical TATA box, suggesting unique regulatory mechanisms.

Purpose of the Study:

• To investigate the cis-acting regulatory elements within the flanking sequences of human U2 and U1 genes.
• To identify and characterize the promoter elements responsible for the high transcription rates of these snRNA genes.

Main Methods:

• Transient expression assays in HeLa cells using modified human U2 genes on SV40 and pUC13 vectors.
• Localization and functional analysis of promoter elements within the 5'-flanking sequences.
• Comparison of enhancer activity with SV40 enhancer and human U1 promoter sequences.

Main Results:

• Transient expression of the human U2 gene did not require the SV40 enhancer.
• A U2 promoter element within the 5'-flanking sequence conferred SV40 enhancer-independent expression.
• This U2 element stimulated transcription in an orientation- and position-independent manner.
• The U2 element could be functionally replaced by the SV40 enhancer or by distal U1 promoter sequences.

Conclusions:

• Human U2 and U1 genes contain functionally equivalent enhancer elements.
• Enhancers are likely a general feature of vertebrate snRNA promoter structure, similar to Xenopus U2 enhancers.