Dynein Light Chain 1 Contributes to Cell Cycle Progression by Increasing Cyclin-Dependent Kinase 2 Activity in Estrogen-Stimulated Cells

Abstract

Progression of hormone-responsive cancers is characterized by deregulation of the cell cycle and cytoskeleton signaling. In addition, development of breast and endometrial cancer is influenced by the stimulatory action of estrogen. Upregulation of dynein light chain 1 (DLC1), a component of cytoskeleton signaling, was recently found to promote tumorigenesis. The purpose of our study was to determine the role that DLC1 up-regulation plays in cell cycle progression. To achieve this goal, we used human breast ductal carcinoma ZR-75 cells overexpressing DLC1 as a model system. We found that ZR-75 cells with up-regulated DLC1 were hypersensitive to estrogen-dependent growth stimulation and that DLC1 had an accelerating effect on the G 1 -S transition and stimulated cyclin-dependent kinase 2 (Cdk2) activity. To better understand the promotion of the G 1 -S transition by DLC1, we sought to identify new DLC1-interacting proteins with roles in cell cycle regulation. Using a modified proteomic strategy, we identified two such DLC1-interacting proteins: Cdk2 and Cip-interacting zinc finger protein 1 (Ciz1). DLC1 was verified to interact with Cdk2 and Ciz1 in vivo. We also showed that down-regulation of DLC1 and Ciz1 reduced both Cdk2 activity and cell cycle progression of breast cancer ZR-75 and MCF-7 and endometrial Ishikawa cancer cells. Further, we showed that overexpression of DLC1 is accompanied by a reduction of nuclear p21 WAF1 . These findings suggest that interactions among DLC1, Cdk2, and Ciz1 play a regulatory role in cell cycle progression of cancer cells presumably by influencing the levels of nuclear p21 WAF1 .

Integration of Estrogen and Wnt Signaling Circuits by the Polycomb Group Protein EZH2 in Breast Cancer Cells

“…The central involvement of estrogen in the development and carcinogenesis of reproductive organs is well established (1,8,9,42,48,55). However, the understanding of the genomic mechanisms of estrogen action continues to evolve (14,42,56,59).…”

Ciz1, a Novel DNA-Binding Coactivator of the Estrogen Receptor α, Confers Hypersensitivity to Estrogen Action

“…Glutathione S-transferase (GST)-Ciz1 full-length and deletion constructs were generated as described earlier (11). To generate an expression vector containing Myc-tagged Ciz1 (Myc-Ciz1) or a Ciz1 expression vector with T7 tag (T7-Ciz1), Ciz1 cDNA was amplified by PCR and cloned into pCMV-Myc vector (Clontech, Palo Alto, CA) or pcDNA3.1 vector (Invitrogen), respectively.…”

“…An earlier study from this laboratory revealed a coactivator function of dynein light chain 1 (DLC1) in targeting the ER to the chromatin of estrogen-inducible genes in breast cancer cells (10). More recently, we showed that DLC1 interacts with a novel protein, Cip-interacting zinc finger protein 1 (Ciz1), and participates in the regulation of cell cycle by increasing cdk2 kinase activity and inducing the G1-S transition (11,12). Despite the emerging significance of Ciz1 in the biology of breast cancer cells, how endogenous Ciz1 is regulated in hormone-responsive cancer cells is unknown.…”

CIZ1-F, an alternatively spliced variant of the DNA replication protein CIZ1 with distinct expression and localisation, is overrepresented in early stage common solid tumours

“…CIZ1-F protein therefore lacks previously characterized functional domains, including the MH3-domain which anchors CIZ1 to the NM [8], and cyclin-binding motifs through which CIZ1 interacts with cyclin A, and which are essential for its DNA replication activity (Figure 1(b)) [6,7]. Other characterized sites of interaction with CDK2, p21 cip1 and YAP are also excluded [15–17], while interaction with CDC6 [18], ERα [12], and dynein light chain [15] might be retained. The interaction sites of the CIZ1 binding factors PDRG1 [19], SH3BP4 [20], and TCF4 [21] are not yet characterized.…”

“…The CIZ1-F specific sequence, encoded by an alternative reading frame (ARF) of exon 12–13, is highlighted in light blue. Also shown are the location of K/RXL cyclin-binding motifs implicated in replication [7] (‘C’), LXXLL ER-interaction motifs (asterisks), and sequences reported for full-length CIZ1 to interact with CDC6 [18], cyclin-dependent kinase 2 (CDK2) [15], cyclins A and E [7], dynein light chain (DYNLL1) [15], estrogen-receptor (ER) [12], enhancer of rudimentary homolog (ERH) [42], p21 [16], and YAP [17]. Note that several of these interactions were discovered in mouse CIZ1, and that the reported interaction between ER and CIZ1 is not via a domain that includes LXXLL [12].…”