Biology subjects

Koulouras, G.

Publications and source records attributed to Koulouras, G..

5 recordsLinked to original sources

bioRxiv2025

Quantum implementation of multi-pattern string matching for k-mer detection

MotivationThe exponential growth of publicly available genomic data has created unprecedented opportunities for sequence-based discovery. Locating specific k-mers is fundamental to diverse applications, including metagenomic classification, pathogen and cancer detection, and variant calling yet efficient identification of multiple k-mer patterns across large sequencing data and massive databases remains a significant computational challenge. MethodWe implement two quantum algorithms for DNA multi pattern string matching for k-mer detection based on Grovers amplitude amplification with quantum random access memory (QRAM). The first algorithm uses an enumerate-m oracle that sequentially checks a loaded text substring against all m patterns achieving O({surd}S) query complexity for S text positions but requiring O(m{middle dot}L) work per oracle call. The second algorithm employs nested Grover search with an outer loop over text positions and an inner loop over pattern space, reducing oracle complexity to O(L) while performing O({surd}S {middle dot} {surd}m) in total. ResultsWe present two quantum implementations of multi-pattern string matching tailored for k-mer detection. Leveraging quantum parallelism and Grover-inspired search primitives, our methods accelerate dictionary-based pattern matching, particularly in contexts involving large sequences, such as genomic data, and extensive pattern sets. ConclusionsWhile implementation challenges such as QRAM overhead remain, this study demonstrates both the promise and current limitations of quantum-enhanced string matching, establishing a foundational step toward quantum readiness in bioinformatics. Availability and implementationTo maximize accessibility and practical use, we provide our methodology at: https://github.com/Georgakopoulos-Soares-lab/quantum-multi-motif-finder

bioinformatics↗

bioRxiv2023

Cancer-associated fibroblasts produce matrix-bound vesicles that influence endothelial cell function

Intercellular communication between different cell types in solid tumors contributes to tumor growth and metastatic dissemination. The secretome of cancer-associated fibroblasts (CAFs) plays major roles in these processes. Using human mammary CAFs, we unveil a mechanism of cell-cell communication between CAFs with myofibroblast phenotype and endothelial cells (ECs) based on intercellular protein transfer through extracellular vesicles (EVs). CAFs transfer proteins to ECs, including plasma membrane receptors, which we have identified by using mass spectrometry- based proteomics. Using THY1 as an example of transferred plasma membrane-bound protein, we show that CAF-derived proteins can influence how ECs interact with other cell types. Here, we show that CAFs produce high amounts of matrix-bound EVs that have a key role in protein transfer. Hence, our work paves the way for further studies to understand how CAF-derived matrix-bound EVs influence tumor pathology by regulating functions of neighboring cancer, stromal and immune cells. One sentence summaryCAFs with a myofibroblastic-like phenotype transfer proteins to ECs, including plasma membrane receptors, through matrix-bound EVs

cancer biology↗

bioRxiv2022

Purine-rich RNA sequences in the 5'UTR site-specifically regulate eIF4A1-unwinding through eIF4A1-multimerisation to facilitate translation

Oncogenic translational programmes underpin cancer development and are often driven by dysregulation of oncogenic signalling pathways that converge on the eukaryotic translation initiation (eIF) 4F complex. Altered eIF4F activity promotes translation of oncogene mRNAs that typically contain highly structured 5UTRs rendering their translation strongly dependent on RNA unwinding by the DEAD-box helicase eIF4A1 subunit of the eIF4F complex. While eIF4A1-dependent mRNAs have been widely investigated, it is still unclear how highly structured mRNAs recruit and activate eIF4A1 unwinding specifically to facilitate their preferential translation. Here, we show that RNA sequence motifs regulate eIF4A1 unwinding activity in cells. Our data demonstrate that eIF4A1-dependent mRNAs contain AG-rich motifs within their 5UTR which recruit and stimulate eIF4A1 unwinding of localised RNA structure to facilitate mRNA translation. This mode of eIF4A1 regulation is used by mRNAs encoding components of mTORC-signalling and cell cycle progression and renders these mRNAs particularly sensitive to eIF4A1-inhibition. Mechanistically, we show that binding of eIF4A1 to AG-rich sequences leads to multimerization of eIF4A1 with eIF4A1 subunits performing distinct enzymatic activities. Our structural data suggest that RNA-binding of multimeric eIF4A1 induces conformational changes in the RNA substrate resulting in an optimal positioning of eIF4A1 proximal to the RNA duplex region that supports efficient unwinding. Hence, we conclude a model in which mRNAs utilise AG-rich sequences to specifically recruit eIF4A1, enabling assembly of the helicase-active multimeric eIF4A1 complex, and positioning these complexes proximal to stable localised RNA structure allowing ribosomal subunit scanning.

molecular biology↗

bioRxiv2020

Significant non-existence of sequences in genomes and proteomes

Nullomers are minimal-length oligomers absent from a genome or proteome. Although research has shown that artificially synthesized nullomers have deleterious effects, there is still a lack of a strategy for the prioritisation and classification of non-occurring sequences as potentially malicious or benign. In this work, by using Markovian models with multiple-testing correction, we reveal significant absent oligomers which are statistically expected to exist. This strongly suggests that their absence is due to negative selection. We survey genomes and proteomes covering the diversity of life, and find thousands of significant absent sequences. Common significant nullomers are often mono- or dinucleotide tracts, or palindromic. Significant viral nullomers are often restriction sites, and may indicate unknown restriction motifs. Surprisingly, significant mammal genome nullomers are often present, but rare, in other mammals, suggesting that they are suppressed but not completely forbidden. Significant human nullomers are rarely present in human viruses, indicating viral mimicry of the host. More than 1/4 of human proteins are one substitution away from containing a significant nullomer. We provide a web-based, interactive database of significant nullomers across genomes and proteomes.

bioinformatics↗

bioRxiv2020

Metabolic control of tumour extracellular matrix production in cancer-associated fibroblasts

TElevated production of collagen-rich extracellular matrix (ECM) is a hallmark of cancer associated fibroblasts (CAFs) and a central driver of cancer aggressiveness. How to target ECM production to oppose cancer is yet unclear, since targeting CAFs has been shown to restrain but also promote cancer progression. Metabolic rewiring is a hallmark of CAFs. Here we find that proline, which is a highly abundant amino acid in collagen proteins, is newly synthesised from glutamine to make tumour collagen in breast cancer xenografts, and that its production is elevated in breast cancer CAFs. PYCR1 is the rate-limiting enzyme for proline synthesis and is highly expressed in the tumour stroma of breast cancer patients and in CAFs. Reducing PYCR1 levels in CAFs is sufficient to reduce tumour collagen production, tumour growth and metastatic spread in vivo and cancer cell proliferation in vitro. PYCR1 and COL1A1 are overexpressed in patients with invasive ductal carcinoma with poor prognosis. Both collagen and glutamine-derived proline synthesis in CAFs are enhanced by increased pyruvate dehydrogenase-derived acetyl-CoA levels, via gene expression regulation through the epigenetic regulator histone acetyl transferase EP300. Altogether, our work unveils unprecedented roles of CAF metabolism to support pro-tumorigenic collagen production. PYCR1 is a recognised cancer cell vulnerability and potential target for therapy, hence, our work provides evidence that targeting PYCR1 in tumours may have the additional benefit of halting the production of pro-tumorigenic ECM.

cancer biology↗