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Mapping and Direct Sequencing of the Non-Canonical Cap Code

Project description

Understanding the non-canonical cap code

mRNAs are regulated through their sequence, promoter, and modifications. The 5’ cap (m7G) is the most well-known modification, playing a role in mRNA stability and translation. However, recent discoveries of non-canonical caps, such as NAD+ and NADH, suggest the existence of a complex ‘cap code’. Current methods for identifying cap structures are limited. The ERC-funded MaDCap project aims to address this by developing a novel single-molecule method to directly sequence native caps and their complete RNA transcripts. The project will characterise the cap-ome across various tissues and developmental stages, creating a detailed temporal and spatial atlas of capped RNAs. This work will uncover the functions of non-canonical caps and provide insights into the non-canonical cap code.

Objective

From their creation to their degradation, mRNAs are under extensive regulation. This regulation is directed not only by their nucleotide sequence and their promoter but also by post- and co-transcriptional modifications attached to the RNA. One of the most ubiquitous of these modifications in eukaryotes is the 5' cap typically a methylated guanine (m7G) attached inversely to the first transcribed nucleotide. Several decades of research have revealed the m7G cap as an interface for regulating stability, splicing, polyadenylation, localization, and translation. The m7G cap was long presumed to be the only functional cap in eukaryotes, but this view was recently overturned by the discovery of the non-canonical nicotinamide adenine dinucleotide (NAD+) cap. Following this, several other eukaryotic cap structures were discovered: NADH, flavin adenine dinucleotide (FAD), uridine diphosphate glucose (UDP-Glc), and uridine diphosphate N-acetylglucosamine (UDP-GlcNAc). The function of most non-canonical caps is unknown, but their presence suggests the existence of a regulatory cap code.

Currently, the complete cap structure can only be identified through bulk methods that cleave caps from their transcripts, thereby losing the link between mRNAs and their specific caps. For NAD-caps enrichment techniques exist that can be followed by sequencing, but no such method exists for other non-canonical caps, and no sequencing method exists that can identify more than one cap. This limitation is a significant obstacle in understanding the cap code and the function of its more enigmatic members.

The objective of this project is to 1) develop a novel single-molecule method that can directly sequence native caps with their full-length RNA transcripts, 2) use this method to characterize the cap-ome across tissues and development, and 3) use the resulting temporal and spatial atlas of capped RNAs to determine the function of non-canonical caps and understand the non-canonical cap code

Fields of science (EuroSciVoc)

Keywords

Programme(s)

Topic(s)

Funding Scheme

HORIZON-ERC - HORIZON ERC Grants

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Call for proposal

(opens in new window) ERC-2022-COG

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Host institution

UNIVERSITETET I OSLO
Net EU contribution
€ 2 000 000,00
Address
PROBLEMVEIEN 5-7
0313 Oslo
Norway
Region
Norge Oslo og Viken Oslo
Activity type
Higher or Secondary Education Establishments
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Total cost
€ 2 000 000,00

Beneficiaries (1)