Saccharomyces cerevisiae DNA polymerase δ (Pol δ) and DNA polymerase ε (Pol ε) are replicative DNA polymerases at the replication fork. Both enzymes are stimulated by PCNA, although to different levels. To understand why and to explore the interaction with PCNA, we compared Pol δ and Pol ε in physical interactions with PCNA and nucleic acids (with or without RPA), and in functional assays measuring activity and processivity. Using surface plasmon resonance technique, we show that Pol ε has a high affinity for DNA, but a low affinity for PCNA. In contrast, Pol δ has a low affinity for DNA and a high affinity for PCNA. The true processivity of Pol δ and Pol ε was measured for the first time in the presence of RPA, PCNA and RFC on single-stranded DNA. Remarkably, in the presence of PCNA, the processivity of Pol δ and Pol ε on RPA-coated DNA is comparable. Finally, more PCNA molecules were found on the template after it was replicated by Pol ε when compared to Pol δ. We conclude that Pol ε and Pol δ exhibit comparable processivity, but are loaded on the primer-end via different mechanisms.

Telomere length is associated with mutation status of the immunoglobulin heavy chain variable (IGHV) gene and clinical course in B-cell chronic lymphocytic leukemia (B-CLL). In a B-CLL cohort of 152 patients, we analyzed telomere length, genomic aberrations, IGHV mutation status, CD38 and ZAP-70 expression to study the prognostic impact and associations among these factors. An inverse correlation existed between telomere length and IGHV homology (P < .001), CD38 (P < .001), and ZAP-70 expression (P ‫؍‬ .01). Patients with telomere lengths below median (ie, "short telomeres") and above median (ie, "long telomeres") had similar incidences of genomic aberrations (74% vs 68%), 13q؊ (57% vs 49%), and ؉12q (5% vs 12%). In contrast, 13q؊ as a single aberration was more frequent in patients with long telomeres (51% vs 21%; P ‫؍‬ .006), whereas 11q؊ (27% vs 9%; P ‫؍‬ .014), 17p؊ (17% vs 0%; P < .001), and 2 or more genomic aberrations (39% vs 8%; P < .001) were more frequent in patients with short telomeres.Compared with patients with long telomeres, treatment-free survival (TFS) and overall survival (OS) was significantly shorter (P < .001 and P ‫؍‬ .015, respectively) in the group with short telomeres, and telomere length was an independent prognostic indicator for TFS. IntroductionB-cell chronic lymphocytic leukemia (B-CLL), the most common leukemia in adults in the Western world, is characterized by a monoclonal expansion of mature B lymphocytes expressing CD19, CD5, and CD23 on the cell surface. 1 B-CLL is a clinically heterogeneous disease with survival times ranging from months to normal lifespan. 2 As a consequence of the variable clinical course, it has become very crucial to identify reliable prognostic factors useful in planning therapeutic strategies and predicting the outcome. A number of biological features of B-CLL have been described, and several of them can be used to discern different groups of patients with significant differences in clinical course and outcome. The immunoglobulin heavy chain variable (IGHV) gene mutation status analysis reveals 2 subgroups of B-CLL, [3][4][5] with a more favorable clinical course for patients with mutated IGHV genes. [6][7][8][9] The surface marker CD38 has been proposed as a surrogate marker for IGHV gene mutation status in B-CLL, 3 but the association between these markers was shown to be rather weak. 7-11 Furthermore, CD38 has been shown to be an independent prognostic marker, although no consensus has been reached concerning cut-off levels. 7,8,[11][12][13] Expression of the protein tyrosine kinase ZAP-70 is strongly associated with IGHV gene mutation status and can be used as an independent prognostic factor. 14-16 Although discordant results have been reported lately, certain IGHV gene usage (eg, and presence of high-risk genomic aberrations (eg, 11qϪ and 17pϪ) can explain these findings at least in part. 17,18 In mature B-cell neoplasms, telomere length correlates with histopathogenesis according to the germinal center. 19 This feature includes B-CLL showing a...

B-cell chronic lymphocytic leukemia (CLL) consists of 2 prognostic entities where cases with mutated immunoglobulin V H genes have better outcome than unmutated cases. V H -mutated CLLs display longer telomeres compared with unmutated cases and telomere length has been indicated to predict outcome, although the prognostic value of telomere length has not been fully established in CLL. We analyzed telomere length, V H gene mutation status, and clinical parameters in a large series of CLL. Telomere length was assessed by quantitative polymerase chain reaction (PCR), giving a very good correlation to telomere length estimated by Southern blotting (P < .001). The prognostic information given by mutation status (n ‫؍‬ 282) and telomere length (n ‫؍‬ 246) was significant (P < .001, respectively). Telomere length was a prognostic factor for stage A (P ‫؍‬ .021) and stage B/C (P ‫؍‬ .018) patients, whereas mutation status predicted outcome only in stage A patients (P < .001). Furthermore, mutated CLLs were subdivided by telomere length into 2 groups with different prognoses (P ‫؍‬ .003), a subdivision not seen for unmutated cases (P ‫؍‬ .232). Interestingly, the V H -mutated group with short telomeres had an overall survival close to that of the unmutated cases. Thus, by combining V H mutation status and telomere length, an improved subclassification of CLL was achieved identifying previously unrecognized patient groups with different outcomes. IntroductionThe end structures of the chromosomes, the telomeres, are composed of a repetitive DNA sequence, (TTAGGG) n , and specific proteins bound to the DNA. 1,2 The telomeres protect the chromosomes from degradation, prevent end-to-end fusions, and are crucial for control of replicative senescence. In humans, the telomeres have an average length of 5 kilobases (kb) to 15 kb and in normal somatic cells the telomeric DNA shortens with 100 base pair (bp) to 200 bp every cell division due to the end-replication problem. [3][4][5] The erosion of the telomeres can be counteracted by telomerase, an enzyme that adds TTAGGG repeats to the chromosomal ends. 6 Telomere maintenance, usually executed by telomerase, is a prerequisite for an extended or infinite cellular lifespan, and studies of telomere dynamics have been in focus ever since it was shown that telomerase activity is present in almost 90% of all malignant tumors. [7][8][9] The nearly exclusive presence of telomerase in tumor cells has made the enzyme a theoretically attractive target for cancer therapy. In contrast, telomerase is restricted to a few normal cell types in humans, including germ cells, stem cells, activated lymphocytes, and epithelial cells with high reproductive demand. [10][11][12][13][14] Additionally, during the germinal center (GC) reaction in lymph nodes a high level of telomerase activity is expressed in the GC B cells accompanied by a unique telomere lengthening process not observed in other cells in vivo. [15][16][17] Telomere length reduction has been found with increasing age and was recently impli...