DYNLL1 Human

What is the basic structure and cellular localization of human DYNLL1?

DYNLL1 is a homodimeric sequence-specific chaperone that facilitates the ordered oligomerization of more than a hundred protein targets . As an important constituent of the motor protein complex, DYNLL1 is encoded by the DYNLL1 gene in humans . The protein exhibits wide cellular distribution, being present in both the cytoplasm (as part of dynein complexes) and the nucleus, where it participates in various cellular processes including DNA damage response mechanisms.

How does DYNLL1 interact with its binding partners at the molecular level?

DYNLL1 interacts with numerous proteins through a short linear consensus motif sequence, typically (K/R)XTQT . This structural feature enables DYNLL1 to serve as a hub protein that can interact with numerous partners. For viral proteins, this interaction occurs through the same conserved short linear motif (SLiM), allowing them to hijack cellular machinery . The protein contains distinct binding regions that facilitate protein-protein interactions, including its ability to regulate MRE11 by binding to its N-terminal fragment (residues 1-181) and another fragment (residues 293-483) encompassing a DNA binding domain .

What are the major cellular pathways involving DYNLL1?

DYNLL1 extensively participates in modulating various cellular functions including:

• Intracellular trafficking and cargo transport

• Apoptosis regulation

• DNA damage response and repair pathways, particularly in regulating DNA end resection

• Primary cilia function and retrograde intraflagellar transport as part of the cytoplasmic dynein-2 (CD2) complex

• Cell cycle regulation, with impacts on cellular proliferation when dysregulated

What role does DYNLL1 play in cancer progression?

DYNLL1 demonstrates context-dependent roles in cancer progression. It is frequently upregulated in several cancer types:

Mechanistically, silencing DYNLL1 can inhibit cancer cell proliferation while promoting cell cycle arrest and apoptosis, accompanied by elevated caspase3 activity, reduced Bcl-2 expression, and increased Bax expression .

How does DYNLL1 contribute to developmental processes?

DYNLL1 is essential for proper development, particularly in bone formation. Studies with Dynll1-deficient mouse models have revealed:

• Germline Dynll1 knockout mice exhibit severe ciliopathy-like phenotypes similar to mice lacking other CD2 subunits

• Limb mesoderm-specific loss of Dynll1 results in severe bone shortening resembling human short-rib thoracic dystrophy syndrome (SRTD) patients

• DYNLL1 promotes endochondral bone formation by regulating intraflagellar dynein function in primary cilia

• The loss of Dynll1 leads to significant thickening of primary cilia and cilia signaling defects

What are the implications of DYNLL1 mutations in human disease?

Mutations affecting DYNLL1 or its regulatory pathways can contribute to several pathological conditions:

• As a subunit of the cilia-specific cytoplasmic dynein-2 complex, disruptions in DYNLL1 function can contribute to ciliopathies

• Loss of DYNLL1 can lead to syndromes resembling short-rib thoracic dystrophy (SRTD), characterized by impaired bone growth and potentially life-threatening perinatal respiratory complications

• Maintaining even very low DYNLL1 levels (versus complete knockout) results in significantly attenuated phenotypes, suggesting dosage-dependent effects

How does DYNLL1 regulate DNA damage repair mechanisms?

DYNLL1 plays a sophisticated role in DNA damage repair through multiple mechanisms:

• It is recruited to DNA double-strand breaks (DSBs) in a 53BP1-dependent manner

• DYNLL1 regulates MRE11 activity, which is crucial for DNA end resection

• It can disrupt MRE11 dimerization, thereby impairing its retention on chromatin

• Phosphorylated DYNLL1 blocks Shieldin recruitment by impairing the initiation of DNA end resection

• DYNLL1 functions upstream of G1-dependent end resection necessary for Shieldin recruitment in G1 phase cells

These mechanisms collectively contribute to DNA repair pathway choice and influence sensitivity to PARP inhibitors (PARPi) in cancer cells .

What is known about the regulation of DYNLL1 protein levels?

DYNLL1 protein levels are regulated through several mechanisms:

• It can be ubiquitinated and degraded by E3 ubiquitin ligase PRKN

• According to the UbiBrowser database, E3 ubiquitin ligase PRKN specifically modulates DYNLL1 ubiquitination

• In esophageal squamous cell carcinoma, E3 ubiquitin ligase RNF114 mediates DYNLL1 degradation, influencing cancer progression

• Transcriptional regulation occurs through factors such as ASCIZ (ATMIN), with studies showing that mice lacking this DYNLL1-transcription factor maintain very low DYNLL1 levels

How does DYNLL1 interact with primary cilia function?

DYNLL1 is critical for primary cilia function through several mechanisms:

• It serves as a subunit of the cilia-specific cytoplasmic dynein-2 (CD2) complex

• Loss of Dynll1 leads to partial depletion of other CD2 subunits

• It significantly impacts retrograde intraflagellar transport, with its deficiency causing severe impairment

• DYNLL1 deficiency results in significant thickening of primary cilia and cilia signaling defects

• Interestingly, phenotypes of Dynll1-deficient mice are very similar to entirely cilia-deficient mice, except they never present with polydactyly and retain relatively higher signaling outputs in parts of the hedgehog pathway

What are the current approaches for studying DYNLL1 expression and function?

Researchers employ various techniques to study DYNLL1:

• Expression analysis: RT-qPCR and western blot to detect mRNA and protein expressions

• Functional analysis: Cell proliferation assays (CCK-8), EdU staining, and colony formation assays

• Protein-protein interactions: Immunoprecipitation to evaluate interactions with binding partners

• Binding affinity measurements: Microscale thermophoresis (MST) to determine binding constants (Kd) for protein-protein interactions

• In vivo studies: Generation of knockout and conditional knockout mouse models

• Database analysis: Utilization of databases like UALCAN and UbiBrowser to analyze expression patterns and regulatory mechanisms

How can researchers effectively modulate DYNLL1 expression or function in experimental settings?

Several approaches can be employed to modify DYNLL1 expression or function:

• RNA interference: Transfection of short hairpin RNAs (sh-DYNLL1) for silencing DYNLL1 expression

• CRISPR-Cas9 gene editing: Generation of knockout cell lines or animal models

• Conditional knockout models: Tissue-specific deletion using Cre-lox systems (e.g., limb mesoderm-specific knockout)

• Expression of modified DYNLL1 variants: Using constructs like DYNLL1-FHA (forced localization) or phosphomimetic mutants (DYNLL1-S88D)

• Inhibition of specific functions: Using inhibitors targeting MRE11's endonuclease or exonuclease activities to dissect DYNLL1-related pathways

What techniques are useful for studying DYNLL1's role in DNA damage response?

For investigating DYNLL1's role in DNA damage response, researchers can employ:

• Foci formation assays: Monitoring the formation of DYNLL1, MRE11, RAD51, or SHLD1 foci at DNA damage sites

• DNA end resection assays: qPCR-based methods to measure single-stranded DNA generated from specific double-strand breaks

• Engineered nuclease systems: Using systems like ER-AsiSI to induce site-specific DNA damage

• Cell cycle-specific analyses: Distinguishing between G1 and other cell cycle phases when analyzing DYNLL1 functions

• Sensitivity assays: Testing sensitivity to PARP inhibitors (PARPi) to evaluate functional impacts of DYNLL1 modulation

What are the major unresolved questions regarding DYNLL1 function?

Despite significant advances, several questions remain unanswered:

• The complete spectrum of DYNLL1 binding partners and how these interactions are regulated

• Whether bacterial proteins, like viral proteins, contain conserved SLiM sequences through which they bind to DYNLL1

• The precise mechanism by which DYNLL1 coordinates with other factors in regulating DNA repair pathway choice

• How DYNLL1's diverse functions in different cellular compartments are coordinated and regulated

• The therapeutic potential of targeting DYNLL1 in various disease contexts, particularly cancer

How might therapeutic targeting of DYNLL1 be approached in cancer or other diseases?

Targeting DYNLL1 for therapeutic purposes presents several possibilities:

• Direct inhibition of DYNLL1 expression or function in cancers where it promotes proliferation

• Enhancing DYNLL1 degradation through modulation of E3 ubiquitin ligases like PRKN or RNF114

• Developing compounds that interfere with specific DYNLL1 protein-protein interactions

• Combination therapies targeting DYNLL1 and other pathway components, such as using PARP inhibitors alongside DYNLL1 modulation

• Exploring the potential of DYNLL1 as a biomarker for disease prognosis or treatment response

What emerging technologies might advance our understanding of DYNLL1?

Cutting-edge approaches that could enhance DYNLL1 research include:

• Single-cell technologies to understand cell-to-cell variability in DYNLL1 function

• Cryo-electron microscopy for detailed structural analysis of DYNLL1 complexes

• Proximity labeling approaches to comprehensively identify DYNLL1 interactors in different cellular contexts

• Advanced genomic editing using prime editing or base editing for more precise genetic modifications

• Computational approaches integrating multi-omics data to predict new DYNLL1 functions and interactions