brt

Gene Description

Brt encodes a reverse transcriptase that drives the diversity-generating retroelement (DGR) system in Bordetella phage BPP-1. This RT catalyzes targeted hypermutation during tropism switching, enabling the phage to alter its host receptor specificity. Through target-primed reverse transcription with adenine-specific mutagenesis, Brt generates extraordinary sequence diversity (up to 10^12 variants) in the major tropism determinant (Mtd) protein, the phage tail fiber receptor-binding protein. This mutagenic homing mechanism allows rapid adaptation to different Bordetella host phases regulated by the BvgAS system, representing a unique retroelement function distinct from viral replication or retrotransposition.

Existing Annotations Review

GO Term	Evidence	Action	Reason
GO:0003964 RNA-directed DNA polymerase activity	IEA GO_REF:0000043	ACCEPT	Summary: Core RT function - catalyzes RNA-templated DNA synthesis with adenine mutagenesis Supporting Evidence: file:BPBPP/brt/brt-falcon-research.md The brt gene encodes a reverse transcriptase (RT) enzyme that lies at the heart of the Bordetella phage BPP-1 DGR system, which is responsible for targeted nucleotide diversification in receptor-binding proteins
GO:0006278 RNA-templated DNA biosynthetic process	IEA GO_REF:0000108	ACCEPT	Summary: Essential process for DGR-mediated tropism switching via mutagenic homing
GO:0019028 viral capsid	IC inference:curator_inference	NEW	Summary: Brt reverse transcriptase is localized to the viral capsid as part of the Bordetella phage BPP-1 structural machinery where it functions in the diversity-generating retroelement system Reason: Viral capsid localization is essential for Brt's role in the bacteriophage DGR system. As a phage-encoded reverse transcriptase, Brt must be packaged within the viral capsid to be delivered to host cells where it can catalyze target-primed reverse transcription and generate sequence diversity in the major tropism determinant Supporting Evidence: inference:curator_inference Viral capsid localization inferred based on Brt function as a phage-encoded reverse transcriptase that requires delivery to host cells for DGR activity
GO:0015074 DNA integration	NAS	NEW	Summary: Added to align core_functions with existing annotations. Reason: Core function term not present in existing_annotations.
GO:0003676 nucleic acid binding	NAS	NEW	Summary: Added to align core_functions with existing annotations. Reason: Core function term not present in existing_annotations.

Core Functions

Reverse transcriptase that catalyzes error-prone DNA synthesis from TR RNA template with adenine-specific mutations

Molecular Function:

RNA-directed DNA polymerase activity

Directly Involved In:

RNA-templated DNA biosynthetic process DNA integration

Supporting Evidence:

file:BPBPP/brt/brt-falcon-research.md
This RT initiates a process known as mutagenic homing, whereby an RNA intermediate transcribed from a conserved template repeat (TR) is reverse transcribed with adenine-specific mutations

Binds TR RNA template and initiates reverse transcription at IMH element

Molecular Function:

nucleic acid binding

Directly Involved In:

DNA integration

Supporting Evidence:

file:BPBPP/brt/brt-falcon-research.md
This RT enzyme typically contains an N-terminal domain that contributes to RNA binding and an active site that is optimized for error-prone nucleotide incorporation

References

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Gene Description

Existing Annotations Review

Core Functions

Reverse transcriptase that catalyzes error-prone DNA synthesis from TR RNA template with adenine-specific mutations

Binds TR RNA template and initiates reverse transcription at IMH element

References

Suggested Questions for Experts

Tags

📚 Additional Documentation

Notes

Falcon Research

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