Outcomes Post Beyond Total Mesorectal Excision Plane Resections Following Setting up Complex Colorectal Cancer Service in a District General Hospital.

Background: This study aims to validate the feasibility of a hub-and-spoke model for pelvic exenteration (PE) surgery while upholding favorable patient outcomes. Methods: A retrospective analysis of patients undergoing PE at our trust October 2017 and December 2023 was conducted. Descriptive statistics and Kaplan-Meier survival analysis were employed. Results: Sixty-seven patients underwent PE during the study period, mainly for locally advanced colorectal cancer (n=61, 91.04%). Minimally invasive surgery was performed in 16 cases (Robotic 3, 4.47% / Laparoscopic 13, 19.40) while the rest of patients 51 had open surgery (75.11%). Median hospital stay was 12 days (range:8-20). While 24 patients (35.82%) developed major complications (CD III-IV) post-surgery, there were no mortalities associated with pelvic exenteration in this study. Of the 67 patients undergoing surgery with curative intent, negative margins (R0 resection) were achieved in 57 patients (85.12%). This is comparable to outcomes reported by the PelvEx collaborative (85.07% versus 79.8%). At a median follow-up of 22 months, 15 patient (22.38%) recurred with 10.44% local recurrence rate. The 2 years overall and disease-free survival were 85.31% and 77.0.36%, respectively. Conclusion: Our study suggests that a nascent PE service, supported by specialist expertise and resources, can achieve good surgical outcomes within a district general hospital.

Degradation of neurodegenerative disease-associated TDP-43 aggregates and oligomers via a proteolysis-targeting chimera.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) associated with TAR DNA-binding protein 43 (TDP-43) aggregation has been considered as a lethal and progressive motor neuron disease. Recent studies have shown that both C-terminal TDP-43 (C-TDP-43) aggregates and oligomers were neurotoxic and pathologic agents in ALS and frontotemporal lobar degeneration (FTLD). However, misfolding protein has long been considered as an undruggable target by applying conventional inhibitors, agonists, or antagonists. To provide this unmet medical need, we aim to degrade these misfolding proteins by designing a series of proteolysis targeting chimeras (PROTACs) against C-TDP-43. METHODS: By applying filter trap assay, western blotting, and microscopy imaging, the degradation efficiency of C-TDP-43 aggregates was studied in Neuro-2a cells overexpressing eGFP-C-TDP-43 or mCherry-C-TDP-43. The cell viability was characterized by alarmarBlue assay. The beneficial and disaggregating effects of TDP-43 PROTAC were examined with the YFP-C-TDP-43 transgenic C. elegans by motility assay and confocal microscopy. The impact of TDP-43 PROTAC on C-TDP-43 oligomeric intermediates was monitored by fluorescence lifetime imaging microscopy and size exclusion chromatography in the Neuro-2a cells co-expressing eGFP-C-TDP-43 and mCherry-C-TDP-43. RESULTS: Four PROTACs with different linker lengths were synthesized and characterized. Among these chimeras, PROTAC 2 decreased C-TDP-43 aggregates and relieved C-TDP-43-induced cytotoxicity in Neuro-2a cells without affecting endogenous TDP-43. We showed that PROTAC 2 bound to C-TDP-43 aggregates and E3 ligase to initiate ubiquitination and proteolytic degradation. By applying advanced microscopy, it was further shown that PROTAC 2 decreased the compactness and population of C-TDP-43 oligomers. In addition to cellular model, PROTAC 2 also improved the motility of transgenic C. elegans by reducing the C-TDP-43 aggregates in the nervous system. CONCLUSIONS: Our study demonstrated the dual-targeting capacity of the newly-designed PROTAC 2 against both C-TDP-43 aggregates and oligomers to reduce their neurotoxicity, which shed light on the potential drug development for ALS as well as other neurodegenerative diseases.

FDG-PET/CT in colorectal cancer: potential for vascular-metabolic imaging to provide markers of prognosis.

PURPOSE: This study assesses the potential for vascular-metabolic imaging with FluoroDeoxyGlucose (FDG)-Positron Emission Tomography/Computed Tomography (PET/CT) perfusion to provide markers of prognosis specific to the site and stage of colorectal cancer. METHODS: This prospective observational study comprised of participants with suspected colorectal cancer categorized as either (a) non-metastatic colon cancer (M0colon), (b) non-metastatic rectal cancer (M0rectum), or (c) metastatic colorectal cancer (M+). Combined FDG-PET/CT perfusion imaging was successfully performed in 286 participants (184 males, 102 females, age: 69.60 ± 10 years) deriving vascular and metabolic imaging parameters. Vascular and metabolic imaging parameters alone and in combination were investigated with respect to overall survival. RESULTS: A vascular-metabolic signature that was significantly associated with poorer survival was identified for each patient group: M0colon - high Total Lesion Glycolysis (TLG) with increased Permeability Surface Area Product/Blood Flow (PS/BF), Hazard Ratio (HR) 3.472 (95% CI: 1.441-8.333), p = 0.006; M0rectum - high Metabolic Tumour Volume (MTV) with increased PS/BF, HR 4.567 (95% CI: 1.901-10.970), p = 0.001; M+ participants, high MTV with longer Time To Peak (TTP) enhancement, HR 2.421 (95% CI: 1.162-5.045), p = 0.018. In participants with stage 2 colon cancer as well as those with stage 3 rectal cancer, the vascular-metabolic signature could stratify the prognosis of these participants. CONCLUSION: Vascular and metabolic imaging using FDG-PET/CT can be used to synergise prognostic markers. The hazard ratios suggest that the technique may have clinical utility.

The Different Faces of the TDP-43 Low-Complexity Domain: The Formation of Liquid Droplets and Amyloid Fibrils.

Transactive response DNA-binding protein 43 (TDP-43) is a nucleic acid-binding protein that is involved in transcription and translation regulation, non-coding RNA processing, and stress granule assembly. Aside from its multiple functions, it is also known as the signature protein in the hallmark inclusions of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) patients. TDP-43 is built of four domains, but its low-complexity domain (LCD) has become an intense research focus that brings to light its possible role in TDP-43 functions and involvement in the pathogenesis of these neurodegenerative diseases. Recent endeavors have further uncovered the distinct biophysical properties of TDP-43 under various circumstances. In this review, we summarize the multiple structural and biochemical properties of LCD in either promoting the liquid droplets or inducing fibrillar aggregates. We also revisit the roles of the LCD in paraspeckles, stress granules, and cytoplasmic inclusions to date.

Biocompatible Inhibitor Based on Chitosan and Amphiphilic Peptide against Mutant Huntingtin Toxicity.

Huntington's disease (HD) is classified as a protein-misfolding disease correlated with the mutant Huntingtin (mHtt) protein with abnormally expanded polyglutamine (polyQ) domains. Because no effective drugs have yet been reported, attempts to develop better therapy to delay the age of onset are in urgent demand. In this study, an amphiphilic peptide consisting of negatively charged hexaglutamic acid and a stretch of decaglutamine (E6 Q10 ) was chemically synthesized as an inhibitor against polyQ and mHtt toxicity. It is found that E6 Q10 selfassembles into spherical vesicles, as shown by means of TEM, cryoelectron microscopy, and dynamic light scattering. Assembled E6 Q10 prevented the polyQ-rich peptide (KKWQ20 AKK) from forming amyloid fibrils. To enable the cell-penetration ability of E6 Q10 , the E6 Q10 ⋅chitosan complex was generated. It is demonstrated that the complex penetrates cells, interferes with the mHtt oligomerization and aggregation process, and prevents mHtt cytotoxicity. By combining positively charged chitosan and amphiphilic peptides with a negatively charge moiety, a new strategy is provided to develop biocompatible and biodegradable inhibitors against mHtt toxicity.

Nonorthogonal tRNA(cys)(Amber) for protein and nascent chain labeling.

In vitro-transcribed suppressor tRNAs are commonly used in site-specific fluorescence labeling for protein and ribosome-bound nascent chains (RNCs) studies. Here, we describe the production of nonorthogonal Bacillus subtilis tRNA(cys)(Amber) from Escherichia coli, a process that is superior to in vitro transcription in terms of yield, ease of manipulation, and tRNA stability. As cysteinyl-tRNA synthetase was previously shown to aminoacylate tRNA(cys)(Amber) with lower efficiency, multiple tRNA synthetase mutants were designed to optimize aminoacylation. Aminoacylated tRNA was conjugated to a fluorophore to produce BODIPY FL-cysteinyl-tRNA(cys)(Amber), which was used to generate ribosome-bound nascent chains of different lengths with the fluorophore incorporated at various predetermined sites. This tRNA tool may be beneficial in the site-specific labeling of full-length proteins as well as RNCs for biophysical and biological research.

An Optimized Protocol for Packaging Pseudotyped Integrase Defective Lentivirus.

BACKGROUND: A number of integrase defective lentiviral (IDLV) packaging systems have been developed to produce integration deficient lentiviruses for gene delivery and epichromosomal expression. However, despite their growing demand, a comparative study to systemically evaluate the performance efficiency of different mutants on virus packaging and gene expression has not been done. RESULTS: Site-directed mutagenesis was used to generate five integrasedeficient mutants for non-integrative lentiviral packaging (NILVP). The five mutants were then individually incorporated to make different integrase defective lentivirus plasmid packaging mix, keeping other packaging factors constant. CD511B-1, a lentivectorexpressing GFP from an EF1 promoter, was packaged with each of the five different lentivirus packaging mix to make pseudotypedviral particles. The performance and packaging efficiency of each of the integrase deficient mutants was evaluated based on GFP expression in HT1080 cells, while the wild type lentivirus packaging mix was used as a control. Of the five integrase mutant candidates, one with the highestGFP transgene expression level was chosen for further characterization. The non-integrative nature of this candidate was confirmed by quantitative polymerase chain reaction and characterized using both dividing and non-dividing cells. Finally, a detailed standard protocol for NILVP using this integrase defective mutant was developed. CONCLUSIONS: An efficient lentiviral packaging system for producing on-integrative lentivirus was established. This system is compatible with most existing lentivectors and can be used to transduce both dividing and non-dividing cells.

Mechanisms of Membrane Pore Formation by Amyloidogenic Peptides in Amyotrophic Lateral Sclerosis.

Using unbiased atomic-detailed molecular dynamics simulations, the C-terminal fragments of TDP-43 are observed to aggregate and form disordered-toroidal pores in a lipid bilayer. Cytotoxicity of TDP-43 may be inferred from the observation that the membrane pores catalyze lipid flip-flop between bilayer leaflets and conduct water at high rates.

Mechanisms of chorioamnionitis-associated preterm birth: interleukin-1ß inhibits progesterone receptor expression in decidual cells.

In chorioamnionitis (CAM), a major cause of preterm birth (PTB), maternal-fetal inflammation of the decidua and amniochorion cause the release of cytokines that elicit cervical ripening, fetal membrane rupture and myometrial activation. We posit that this inflammatory milieu triggers PTB by inhibiting progesterone receptor (PR) expression and increasing decidual prostaglandin (PG) production. Immunohistochemical staining of decidua detected significantly lower PR levels in decidual cells (DCs) from CAM-complicated PTB. Incubation of DCs with IL-1ß decreased PR expression and significantly increased PGE2 and PGF2α production and COX-2 expression. The addition of PGF2α to DC cultures also suppressed PR expression. However, the COX inhibitor, indomethacin, did not reverse IL-1ß suppression of PR expression in DC cultures. Although IL-1ß treatment activated the NF-KB, ERK1/2 and p38 MAPK signalling cascades in DCs, inhibition of ERK1/2 MAPK signalling alone was sufficient to completely reverse the suppression of PR levels by IL-1ß. These findings suggest that CAM-associated PTB is induced at least in part by IL-1ß-mediated functional progesterone withdrawal.

Strong anion-exchange fast performance liquid chromatography as a versatile tool for preparation and purification of RNA produced by in vitro transcription.

Here we demonstrate the use of strong anion-exchange fast performance liquid chromatography (FPLC) as a simple, fast, and robust method for RNA production by in vitro transcription. With this technique, we have purified different transcription templates from unreacted reagents in large quantities. The same buffer system could be used to readily remove nuclease contamination from the overexpressed pyrophosphatase, the important reagent for in vitro transcription. In addition, the method can be used to monitor in vitro transcription reactions to enable facile optimization of reaction conditions, and we have compared the separation performance between strong and weak anion-exchange FPLC for various transcribed RNAs, including the Diels-Alder ribozyme, the hammerhead ribozyme tRNA, and 4.5S RNA. The functionality of the purified tRNA(Cys) has been confirmed by the aminoacylation assay. Only the purification by strong anion-exchange FPLC has led to the enrichment of the functional tRNA from run-off transcripts as revealed by both enzymatic and electrophoretic analysis.

GOLPH3 modulates mTOR signalling and rapamycin sensitivity in cancer.

Genome-wide copy number analyses of human cancers identified a frequent 5p13 amplification in several solid tumour types, including lung (56%), ovarian (38%), breast (32%), prostate (37%) and melanoma (32%). Here, using integrative analysis of a genomic profile of the region, we identify a Golgi protein, GOLPH3, as a candidate targeted for amplification. Gain- and loss-of-function studies in vitro and in vivo validated GOLPH3 as a potent oncogene. Physically, GOLPH3 localizes to the trans-Golgi network and interacts with components of the retromer complex, which in yeast has been linked to target of rapamycin (TOR) signalling. Mechanistically, GOLPH3 regulates cell size, enhances growth-factor-induced mTOR (also known as FRAP1) signalling in human cancer cells, and alters the response to an mTOR inhibitor in vivo. Thus, genomic and genetic, biological, functional and biochemical data in yeast and humans establishes GOLPH3 as a new oncogene that is commonly targeted for amplification in human cancer, and is capable of modulating the response to rapamycin, a cancer drug in clinical use.

Laparoscopic right hemicolectomy with complete mesocolic excision and D3 lymphadenectomy using the open book approach: a video vignette.

According to the concept of total mesorectal excision for rectal cancer, Hohenberger translated this concept to colonic cancer by introducing complete mesocolic excision (CME). The concept of this surgical technique was further elucidated by Benz et al. in the form of an open book approach. This article presents and demonstrates in a video a case of laparoscopic right hemicolectomy with CME and D3 lymphadenectomy using open book approach in the treatment of a T3N1M0 distal ascending colonic adenocarcinoma. The final pathology report confirmed moderately differentiated adenocarcinoma with a maximum tumor size of 55 mm and 0/60 lymph nodes. The mesocolic fascia was intact and R0 was achieved. The final staging was pT3pN0pM0. However, D3 lymphadenectomy is not universally adopted due to concerns of higher morbidity we believe that with adequate training and supervision CME with D3 LDN is feasible and safe to be offered to all right-sided colorectal cancers with curative intent treatment.

Comparison of early surgical outcomes of robotic and laparoscopic colorectal cancer resection reported by a busy district general hospital in England.

Robotic platforms provide a stable tool with high-definition views and improved ergonomics compared to laparoscopic approaches. The aim of this retrospective study was to compare the intra- and short-term postoperative results of oncological resections performed robotically (RCR) and laparoscopically (LCR) at a single centre. Between February 2020 and October 2022, retrospective data on RCR were compared to LCR undertaken during the same period. Parameters compared include total operative time, length of stay (LOS), re-admission rates, 30-day morbidity. 100 RCR and 112 LCR satisfied inclusion criteria. There was no difference between the two group's demographic and tumour characteristics. Overall, median operative time was shorter in LCR group [200 vs. 247.5 min, p < 0.005], but this advantage was not observed with pelvic and muti-quadrant resections. There was no difference in the rate of conversion [5(5%) vs. 5(4.5%), p > 0.95]. With respect to perioperative outcomes, there was no difference in the overall morbidity, or mortality between RCR and LCR, in particular requirement for blood transfusion [3(3%) vs. 5(4.5%), p 0.72], prolonged ileus [9(9%) vs. 15(13.2%), p 0.38], surgical site infections [5(4%) vs. 5(4.4%), p > 0.95], anastomotic leak [7(7%) vs. 5(4.4%), p 0.55], and re-operation rate [9(9%) vs. 7(6.3%), p 0.6]. RCR had shorter LOS by one night, but this did not reach statistical significance. No difference was observed in completeness of resection but there was a statically significant increase in lymph node harvest in the robotic series. Robotic approach to oncological colorectal resections is safe, with comparable intra- and peri-operative morbidity and mortality to laparoscopic surgery.

Engineered droplet-forming peptide as photocontrollable phase modulator for fused in sarcoma protein.

The assembly and disassembly of biomolecular condensates are crucial for the subcellular compartmentalization of biomolecules in the control of cellular reactions. Recently, a correlation has been discovered between the phase transition of condensates and their maturation (aggregation) process in diseases. Therefore, modulating the phase of condensates to unravel the roles of condensation has become a matter of interest. Here, we create a peptide-based phase modulator, JSF1, which forms droplets in the dark and transforms into amyloid-like fibrils upon photoinitiation, as evidenced by their distinctive nanomechanical and dynamic properties. JSF1 is found to effectively enhance the condensation of purified fused in sarcoma (FUS) protein and, upon light exposure, induce its fibrilization. We also use JSF1 to modulate the biophysical states of FUS condensates in live cells and elucidate the relationship between FUS phase transition and FUS proteinopathy, thereby shedding light on the effect of protein phase transition on cellular function and malfunction.

Tissue-free liquid biopsies combining genomic and methylation signals for minimal residual disease detection in patients with early colorectal cancer from the UK TRACC Part B study.

PURPOSE: Absence of post-operative circulating tumour DNA (ctDNA) identifies resected colorectal cancer (CRC) patients with low recurrence risk for adjuvant chemotherapy (ACT) de-escalation. We present the largest resected CRC cohort to date with tissue-free minimal residual disease (MRD) detection. DESIGN: TRACC included stage I-III resectable CRC patients. Prospective longitudinal plasma collection for ctDNA occurred pre- and post-surgery, post-ACT, every 3m for year 1 and every 6m in years 2 and 3 with imaging annually. The Guardant Reveal assay evaluated genomic and methylation signals. The primary endpoint was 2yr recurrence free survival (RFS) by post-operative ctDNA detection. (NCT04050345) Results: Between December 2016 and August 2022, 1203 were patients enrolled. Plasma samples (n=997) from 214 patients were analysed. 143 patients were evaluable for the primary endpoint; 92 (64.3%) colon, 51 (35.7%) rectal; 2 (1.4%) stage I, 64 (44.8%) stage II, 77 (53.8%) stage III. Median follow-up was 30.3m (95% CI: 29.5-31.3). 2yr RFS was 91.1% in patients with ctDNA not detected post-operatively and 50.4% in those with ctDNA detected (HR 6.5 [2.96-14.5] p<0.0001). Landmark negative predictive value (NPV) was 91.2% (95% CI 83.9-95.9). Longitudinal sensitivity and specificity were 62.1% (95% CI 42.2-79.3) and 85.9% (95% CI 78.9-91.3) respectively. Median lead-time from ctDNA detection to radiological recurrence was 7.3m (IQR 3.3-12.5; n=9). CONCLUSIONS: Tissue-free MRD detection with longitudinal sampling predicts recurrence in stage I-III CRC without need for tissue sequencing. NPV is high supporting ACT de-escalation in patients with ctDNA not detected post-operatively, now being investigated in the UK TRACC Part C study.

A do-it-yourself protocol for simple transcription activator-like effector assembly.

BACKGROUND: TALEs (transcription activator-like effectors) are powerful molecules that have broad applications in genetic and epigenetic manipulations. The simple design of TALEs, coupled with high binding predictability and specificity, is bringing genome engineering power to the standard molecular laboratory. Currently, however, custom TALE assembly is either costly or limited to few research centers, due to complicated assembly protocols, long set-up time and specific training requirements. RESULTS: We streamlined a Golden Gate-based method for custom TALE assembly. First, by providing ready-made, quality-controlled monomers, we eliminated the procedures for error-prone and time-consuming set-up. Second, we optimized the protocol toward a fast, two-day assembly of custom TALEs, based on four thermocycling reactions. Third, we increased the versatility for diverse downstream applications by providing series of vector sets to generate both TALENs (TALE nucleases) and TALE-TFs (TALE-transcription factors) under the control of different promoters. Finally, we validated our system by assembling a number of TALENs and TALE-TFs with DNA sequencing confirmation. We further demonstrated that an assembled TALE-TF was able to transactivate a luciferase reporter gene and a TALEN pair was able to cut its target. CONCLUSIONS: We established and validated a do-it-yourself system that enables individual researchers to assemble TALENs and TALE-TFs within 2 days. The simplified TALE assembly combined with multiple choices of vectors will facilitate the broad use of TALE technology.

Genomic deletion of PTEN is associated with tumor progression and early PSA recurrence in ERG fusion-positive and fusion-negative prostate cancer.

The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) gene is often altered in prostate cancer. To determine the prevalence and clinical significance of the different mechanisms of PTEN inactivation, we analyzed PTEN deletions in TMAs containing 4699 hormone-naïve and 57 hormone-refractory prostate cancers using fluorescence in situ hybridization analysis. PTEN mutations and methylation were analyzed in subsets of 149 and 34 tumors, respectively. PTEN deletions were present in 20.2% (458/2266) of prostate cancers, including 8.1% heterozygous and 12.1% homozygous deletions, and were linked to advanced tumor stage (P < 0.0001), high Gleason grade (P < 0.0001), presence of lymph node metastasis (P = 0.0002), hormone-refractory disease (P < 0.0001), presence of ERG gene fusion (P < 0.0001), and nuclear p53 accumulation (P < 0.0001). PTEN deletions were also associated with early prostate-specific antigen recurrence in univariate (P < 0.0001) and multivariate (P = 0.0158) analyses. The prognostic impact of PTEN deletion was seen in both ERG fusion-positive and ERG fusion-negative tumors. PTEN mutations were found in 4 (12.9%) of 31 cancers with heterozygous PTEN deletions but in only 1 (2%) of 59 cancers without PTEN deletion (P = 0.027). Aberrant PTEN promoter methylation was not detected in 34 tumors. The results of this study demonstrate that biallelic PTEN inactivation, by either homozygous deletion or deletion of one allele and mutation of the other, occurs in most PTEN-defective cancers and characterizes a particularly aggressive subset of metastatic and hormone-refractory prostate cancers.

Mig-6 controls EGFR trafficking and suppresses gliomagenesis.

Glioblastoma multiforme (GBM) is the most common and lethal primary brain cancer that is driven by aberrant signaling of growth factor receptors, particularly the epidermal growth factor receptor (EGFR). EGFR signaling is tightly regulated by receptor endocytosis and lysosome-mediated degradation, although the molecular mechanisms governing such regulation, particularly in the context of cancer, remain poorly delineated. Here, high-resolution genomic profiles of GBM identified a highly recurrent focal 1p36 deletion encompassing the putative tumor suppressor gene, Mig-6. We show that Mig-6 quells the malignant potential of GBM cells and dampens EGFR signaling by driving EGFR into late endosomes and lysosome-mediated degradation upon ligand stimulation. Mechanistically, this effect is mediated by the binding of Mig-6 to a SNARE protein STX8, a protein known to be required for late endosome trafficking. Thus, Mig-6 functions to ensure recruitment of internalized receptor to late endosomes and subsequently the lysosomal degradation compartment through its ability to specifically link EGFR and STX8 during ligand-stimulated EGFR trafficking. In GBM, the highly frequent loss of Mig-6 would therefore serve to sustain aberrant EGFR-mediated oncogenic signaling. Together, these data uncover a unique tumor suppression mechanism involving the regulation of receptor trafficking.

Cotranslational protein folding within the ribosome tunnel influences trigger-factor recruitment.

In recent years, various folding zones within the ribosome tunnel have been identified and explored through x-ray, cryo-electron microscopy (cryo-EM), and molecular biology studies. Here, we generated ribosome-bound nascent polypeptide complexes (RNCs) with different polyalanine (poly-A) inserts or signal peptides from membrane/secretory proteins to explore the influence of nascent chain compaction in the Escherichia coli ribosome tunnel on chaperone recruitment. By employing time-resolved fluorescence resonance energy transfer and immunoblotting, we were able to show that the poly-A inserts embedded in the passage tunnel can form a compacted structure (presumably helix) and reduce the recruitment of Trigger Factor (TF) when the helical motif is located in the region near the tunnel exit. Similar experiments on nascent chains containing signal sequences that may form compacted structural motifs within the ribosome tunnel and lure the signal recognition particle (SRP) to the ribosome, provided additional evidence that short, compacted nascent chains interfere with TF binding. These findings shed light on the possible controlling mechanism of nascent chains within the tunnel that leads to chaperone recruitment, as well as the function of L23, the ribosomal protein that serves as docking sites for both TF and SRP, in cotranslational protein targeting.