Expression Vectors with Insulators for Stable Mammalian Protein Production

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Solution Overview

Problem

Existing expression vectors for recombinant protein production in eukaryotic cells face challenges in efficiently integrating into transcriptionally active hot spots, blocking epigenetic gene silencing, ensuring stable and consistent expression, and supporting high-level production of proteins, particularly in continuous perfusion processes.

Innovation Solution

The expression vectors incorporate specific elements such as promoters, IRES, eukaryotic and bacterial selectable markers, and regulatory elements like enhancers and insulators, flanked by ITR sequences, to enhance integration, stability, and expression efficiency, including configurations like a first expression cassette with enhancers and insulators, and a second cassette with a bacterial selectable marker and replication origin.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional expression vectors are used, then basic protein expression can be achieved, but integration efficiency into transcriptionally active hot spots is low and epigenetic silencing occurs

Engineering Contradiction:

Improveintegration efficiencyVSAvoidprotein production level

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The expression vector is divided into distinct functional cassettes: a first expression cassette containing the GOI with enhancers and insulators for reliable integration, and a second expression cassette with selectable markers for stable maintenance. This segmentation allows each component to be optimized independently for its specific function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Insulator elements are introduced as intermediary sequences between the enhancer and the GOI promoter. These insulators act as chromatin boundary elements that prevent spreading of heterochromatin and block epigenetic silencing, thereby maintaining reliable integration and expression.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If multiple regulatory elements are added to enhance expression, then protein production increases, but vector complexity increases

Engineering Contradiction:

Improveprotein production levelVSAvoidvector structure complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

Regulatory elements are segmented into distinct functional modules: enhancers positioned upstream of the GOI promoter, insulators placed between enhancer and promoter, and polyadenylation signals positioned downstream. This modular arrangement enables systematic optimization of each regulatory function while maintaining overall vector manageability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regulatory elements are strategically positioned at specific locations along the vector to perform localized functions. Enhancers provide strong transcriptional activation at the promoter region, insulators provide chromatin boundary protection at intermediate positions, and polyA signals provide transcript termination at the downstream end. Each element's position is optimized for its specific function.

Inventive Principle:

Principle #3Local quality

3Productivity

If constitutive high-level expression is achieved, then protein production increases, but epigenetic gene silencing occurs leading to loss of expression

Engineering Contradiction:

Improveprotein production levelVSAvoidlong-term expression stability

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

Insulator elements serve as intermediary chromatin boundary structures that physically separate the active transcriptional domain from heterochromatin. These insulators block the spread of repressive chromatin modifications and prevent epigenetic silencing, thereby maintaining constitutive high-level expression over extended periods.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The expression cassette is constructed as a composite genetic element combining multiple functional components: strong promoters, enhancers, insulators, and polyadenylation signals. This composite structure integrates the beneficial properties of each element to achieve both high-level constitutive expression and long-term stability by preventing epigenetic silencing.

Inventive Principle:

Principle #40Composite materials

4Reliability

If traditional expression vectors are used, then basic integration occurs, but integration into transcriptionally active hot spots is inefficient

Engineering Contradiction:

Improveintegration stabilityVSAvoidintegration speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

Enhancer elements are positioned upstream of the GOI promoter to preemptively establish an open chromatin configuration and recruit transcriptional activation machinery before integration occurs. This preliminary chromatin remodeling at the integration site facilitates efficient integration into transcriptionally active hot spots and ensures stable expression from the outset.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12421524B2Expression vectors for eukaryotic expression systems

Publication Date: 2025.09.23 MERCK SHARP & DOHME LLC

AI summary

The invention provides expression vectors for expressing recombinant proteins (e.g., biologics) in mammalian cells. Also provided are host cells comprising the expression vectors, methods of producing the recombinant proteins, and methods of propagating the expression vectors.