[Effects of Cullin1 on the Biological Characteristics of Lung Adenocarcinoma A549 and H1395 Cells]

背景与目的

Cullin1是Cullin家族中有代表性的一员，对细胞周期、转录和信号转导相关蛋白泛素化起重要作用，Cullin1与多种恶性肿瘤的发生发展有着密切的联系。本研究旨在探讨Cullin1对肺腺癌A549和H1395细胞生物功能的影响。

方法

实时荧光定量聚合酶链式反应（polymerase chain reaction, PCR）检测肺腺癌细胞（A549、H358、H1395、H1650）及人正常肺上皮细胞BEAS-2B中Cullin1 mRNA表达，采用siRNA技术干扰Cullin1 mRNA相对高表达的肺腺癌细胞；采用四甲基偶氮唑盐比色法（methyl thiazolyl tetrazolium assay, MTT）、流式细胞术及Transwell实验检测细胞增殖、细胞周期分布、细胞早期凋亡及侵袭和迁移能力；采用Western blot检测基质金属蛋白酶-2（matrix metalloproteinase-2, MMP-2）、基质金属蛋白酶-9（matrix metalloproteinase-9, MMP-9）、组织基质金属酶抑制剂-1（tissue inhibitor of metalloproteinase-1, TIMP-1）、细胞周期蛋白D1（Cyclin D1）、细胞周期蛋白E2（Cyclin E2）、p21和p27蛋白的表达水平。

结果

与BEAS-2B细胞相比，肺腺癌细胞中Cullin1 mRNA均呈高表达，尤其在肺腺癌A549和H1395细胞中相对表达量较高（P < 0.05）；干扰Cullin1后肺腺癌细胞的增殖能力受到了抑制，G₁期细胞增多，S期细胞数目减少，肺腺癌细胞早期凋亡率明显升高（P < 0.05）；肺腺癌细胞的侵袭及迁移能力下降（P < 0.05）；干扰Cullin1后MMP-9、MMP-2、Cyclin D1及Cyclin E2蛋白表达量减少（P < 0.05），而TIMP-1、p21和p27蛋白表达量增多（P < 0.05）。

结论

干扰Cullin1后可抑制肺腺癌A549和H1395细胞的增殖、侵袭和迁移，Cullin1在肺腺癌中发挥促癌作用。

SKP1-like protein, CrSKP1-e, interacts with pollen-specific F-box proteins and assembles into SCF-type E3 complex in 'Wuzishatangju' (Citrus reticulata Blanco) pollen

S-ribonuclease (S-RNase)-based self-incompatibility (SI) mechanisms have been extensively studied in Solanaceae, Rosaceae and Plantaginaceae. S-RNase-based SI is controlled by two closely related genes, S-RNase and S-locus F-box (SLF), located at a polymorphic S-locus. In the SI system, the SCF-type (SKP1-CUL1-F-box-RBX1) complex functions as an E3 ubiquitin ligase complex for ubiquitination of non-self S-RNase. Pummelo (Citrus grandis) and several mandarin cultivars are suggested to utilize an S-RNase-based SI system. However, the molecular mechanism of the non-S-factors involved in the SI reaction is not straightforward in Citrus. To investigate the SCF-type E3 complex responsible for the SI reaction in mandarin, SLF, SKP1-like and CUL1 candidates potentially involved in the SI reaction of ‘Wuzishatangju’ (Citrus reticulata Blanco) were identified based on the genome-wide identification and expression analyses. Sixteen pollen-specific F-box genes (CrFBX1-CrFBX16), one pollen-specific SKP1-like gene (CrSKP1-e) and two CUL1 genes (CrCUL1A and CrCUL1B) were identified and cloned from ‘Wuzishatangju’. Yeast two-hybrid (Y2H) and in vitro binding assays showed that five CrFBX proteins could bind to CrSKP1-e, which is an ortholog of SSK1 (SLF-interacting-SKP1-like), a non-S-factor responsible for the SI reaction. Luciferase complementation imaging (LCI) and in vitro binding assays also showed that CrSKP1-e interacts with the N-terminal region of both CrCUL1A and CrCUL1B. These results indicate that CrSKP1-e may serve as a functional member of the SCF-type E3 ubiquitin ligase complex in ‘Wuzishatangju’.

βTrCP is Required for HIV-1 Vpu Modulation of CD4, GaLV Env, and BST-2/Tetherin

The Human immunodeficiency virus-1 (HIV-1) accessory protein Vpu modulates numerous proteins, including the host proteins CD4 and BST-2/tetherin. Vpu interacts with the Skp, Cullin, F-Box (SCF) ubiquitin ligase through interactions with the F-Box protein βTrCP (1 and/or 2). This interaction is dependent on phosphorylation of S^52,56 in Vpu. Mutation of S^52,56, or inhibition of the SCF, abolishes most Vpu activity against CD4 and partly reduces activity against BST-2/tetherin. Recently, Vpu has also been reported to interact with the clathrin adapter proteins AP-1 and AP-2, and these interactions were also found to be required for BST-2/tetherin antagonism in an S^52,56 -dependent manner. In assays where HIV-1 is pseudotyped with gibbon ape leukemia virus (GaLV Env), Vpu has also been found to prevent GaLV Env from being incorporated into viral particles, but the mechanism for this antagonism is not fully understood. To clarify the role of the βTrCPs in Vpu function we used CRISPR/Cas9 to generate a clonal cell line lacking both βTrCP-1 and -2. Vpu activity against CD4 and GaLV Env was abolished in this cell line, and activity against BST-2/tetherin reduced significantly. Mutation of the S^52,56 residues no longer affected Vpu activity against BST-2/tetherin in this cell line. These data suggest that the primary role of the S^52,56 residues in antagonism of CD4, GaLV Env, and BST-2/tetherin is to recruit the SCF/βTrCP ubiquitin ligase.

Synergistic efficacy of Cullin1 and MMP-2 expressions in diagnosis and prognosis of colorectal cancer

BACKGROUND

Cullin1 and MMP-2 have been identified as important markers in various cancers, but their roles in colorectal cancer (CRC) have remained to be discovered. The aim of this study was to investigate the expression pattern and significance of Cullin1 and MMP-2 in CRC.

METHODS

A total of 470 CRC patients were enrolled. Archival paraffin-embedded CRC tissue samples were used to generate tissue microarray blocks, which were immunohistochemically stained for Cullin1 and MMP-2. Prognostic and predictive role of Cullin1 and MMP-2 expression was evaluated by univariate and multivariate analysis, respectively. Values of p < 0.05 were considered statistically significant.

RESULTS

Cullin1 and MMP-2 protein levels were significantly upregulated in CRC tissues compared with adjacent noncancerous tissues. High tumoral Cullin1 or MMP-2 expression significantly correlated with shorter overall survival (OS), as well as with clinicopathologic characteristics in patients. Multivariate regression analysis showed that high Cullin1 and MMP-2 expressions, separately and together, were independent negative markers of OS.

CONCLUSION

Cullin1 and MMP-2 expressions could be novel diagnostic and prognostic markers for CRC patients.

Evolutionary history of two pollen self-incompatibility factors reveals alternate routes to self-compatibility within Solanum

PREMISE OF THE STUDY

Self-incompatibility (SI) prevents self-fertilization and reduces inbreeding. While SI is common in plants, transitions to self-compatibility (SC) occur frequently. Little is known about the genetic changes and evolutionary steps underlying these shifts.

METHODS

In the Solanaceae, SI is gametophytic, with specificity determined by S-RNases in the pistil and S-locus F-box proteins (SLFs) in pollen. We examined the role of two pollen factors, Cullin1 (CUL1) and SLF-23, in SI → SC transitions in wild tomato species from the Arcanum species group (Solanum arcanum, S. neorickii, and S. chmielewskii). Pollen compatibility was assessed on tester lines that reject pollen lacking functional SLF-23 or CUL1. Complementation tests, gene sequencing, and phylogenetic analyses were used to characterize both functional and nonfunctional alleles.

KEY RESULTS

We found evidence for multiple independent SI → SC transitions. In S. arcanum and S. chmielewskii, SC is caused by loss of pistil S-RNase activity, while in S. neorickii SC is associated with expression of a functional SLF-23 that recognizes the S₉ type S-RNase expressed in its pistils. Interestingly, we found identical deletion mutations in CUL1 exon 7 of S. chmielewskii as previously seen in S. habrochaites.

CONCLUSIONS

Mating system transitions in the Arcanum group have occurred via both pistil loss-of-function and pollen gain-of-function SC mutations. Mutations common to S. chmielewskii and S. habrochaites must have arisen in a common ancestor, possibly to the entire tomato clade, then became fixed in different lineages after loss of pistil-side SI function.

Mutations in two pollen self-incompatibility factors in geographically marginal populations of Solanum habrochaites impact mating system transitions and reproductive isolation

PREMISE OF THE STUDY

Self-incompatibility (SI) is a mechanism that prevents inbreeding in many plant species. The mutational breakdown of SI occurs frequently, yet relatively little is known about the evolutionary steps involved in the progressive loss of pistil and pollen SI function.

METHODS

In Solanaceae, SI is the S-RNase-based gametophytic type. We used SI and SC populations of the wild tomato species Solanum habrochaites to study natural variation for two pollen SI factors: a Cullin1 (CUL1) protein and an S-locus F-box protein (SLF-23). Pollen compatibility was assessed on an allotriploid tester line encoding an S-RNase recognized by SLF-23. Both pollen factors are required for compatibility on this tester line. Complementation tests and gene sequencing were used to identify mutations in CUL1 or SLF-23.

KEY RESULTS

We detected loss-of-function mutations in CUL1 and/or SLF-23 in SC populations collected near the northern and southern geographic margins of this taxon's natural range. Nonmarginal SC and all SI accessions expressed mostly functional alleles of these pollen factors. Comparison of the CUL1 sequences identified several shared deletion mutations present in both northern and southern margin SC accessions.

CONCLUSIONS

Loss-of-function mutations in CUL1 and SLF-23 likely became fixed relatively late during SI to SC transitions, after loss of pistil SI function. Mutations in CUL1 establish unilateral incompatibility with SI populations and strengthen reproductive isolation. Point mutations common to northern and southern SC biotypes likely derive from shared ancestral variants found in more central SI populations.

Cullin1 is up-regulated and associated with poor patients' survival in hepatocellular carcinoma

Cullin1 (Cul1) is a scaffold protein of the ubiquitin E3 ligase Skp1/Cullin1/Rbx1/F-box protein complex, which ubiquitinates a broad range of proteins involved in cell-cycle progression, signal transduction, and transcription. To investigate the role of Cul1 in the development of hepatocellular carcinoma (HCC), we evaluated the Cul1 expression by immunohistochemistry using a tissue microarray (TMA) containing 90 cases HCC tissues and paired adjacent non-cancerous tissues. We analyzed the correlation between Cul1 expression and clinicopathologic variables and patients survival using two independent HCC cohorts TMA. Our data showed that Cul1 expression was apparently increased in HCC tissues compared with paired adjacent non-tumor tissues. We also demonstrated that Cul1 staining was significantly correlated with tumor size, histology grade and TNM stage. Furthermore, we showed a strong correlation between high Cul1 expression and worse 5-year overall and disease-specific survival rates in HCC patients. Finally, univariate and multivariate Cox proportional hazards regression analysis investigated that high Cul1 expression was a strong independent prognostic indicator of HCC. Our data indicated that Cul1 may be an important prognosis marker for human HCC.

High expression of Cullin1 indicates poor prognosis for NSCLC patients

BACKGROUND

Cullin1 is a scaffold protein of the ubiquitin E3 ligase Skp1/Cullin1/Rbx1/F-box protein complex which ubiquitinates a broad range of proteins participating in biochemical events like cell-cycle progression, signal transduction, and transcription. Cullin1 is involved in the progression of several cancers, such as melanoma, breast cancer, and gastric cancer.

METHODS

To investigate the role of Cullin1 in the development of non-small-cell lung cancer (NSCLC), we examined the expression of Cullin1 in 8-paired fresh NSCLC tissues. We then constructed immunohistochemistry (IHC) on 114 paraffin-embedded slices and evaluated the correlation between Cullin1 expression and clinicopathologic variables, as well as patients' overall survival.

RESULTS

We found that Cullin1 was highly expressed in NSCLC tissues and significantly associated with NSCLC's histological differentiation (P=0.002), clinical stage (P=0.010) and Ki-67 (P=0.021). Furthermore, we showed a strong correlation between high Cullin1 expression and worse overall survival rates in NSCLC patients (P<0.001). Cox regression analysis revealed that Cullin1 expression was an independent prognostic factor to predict 5-year patient outcome in NSCLC cancer (P=0.033).

CONCLUSION

These data suggested that Cullin1 might promote the progression of NSCLC and be a biotarget for NSCLC's therapy.

The role of a pollen-expressed Cullin1 protein in gametophytic self-incompatibility in Solanum

We previously isolated a pollen factor, ui6.1, which encodes a Cullin1 protein (CUL1) that functions in unilateral interspecific incompatibility (UI) in Solanum. Here we show that CUL1 is also required for pollen function in self-incompatibility (SI). We used RNA interference (RNAi) to reduce CUL1 expression in pollen of Solanum arcanum, a wild SI tomato relative. Hemizygous T0 plants showed little or no transmission of the transfer DNA (T-DNA) through pollen when crossed onto nontransgenic SI plants, indicating that CUL1-deficient pollen are selectively eliminated. When crossed onto a related self-compatible (SC) accession lacking active S-RNase, pollen transmission of the T-DNA followed Mendelian ratios. These results provide further evidence for functional overlap between SI and UI on the pollen side and suggest that CUL1 mutations will reinforce SI-to-SC transitions in natural populations only if preceded by loss of pistil S-RNase expression.