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L Pellizzari

Publications and source records attributed to L Pellizzari.

30 records · Page 2Linked to original sources
PubMed1997

Glyceraldehyde 3-phosphate-induced DNA or protein modifications severely inhibit the protein/DNA interaction.

In this study, the effect of the reducing sugar glyceraldehyde 3-phosphate on protein/DNA interaction has been investigated. Treatment with glyceraldehyde 3-phosphate of oligonucleotides recognized by various transcription factors severely inhibits protein binding. The inhibitory effect is time and dose-dependent. Treatment with glyceraldehyde 3-phosphate of the homeodomain protein TTF-1 HD has also an inhibitory effect on the interaction with DNA, again in a time and dose-dependent manner. These "in vitro" effects could have "in vivo" counterparts and therefore contribute to molecular alterations observed either when intracellular protein are exposed to high doses of reducing sugars (i.e. in diabetes) or after a long time exposure (i.e. in Gzero-arrested cells during aging).

Animals↗
PubMed1997

TRANSCRIPTION FACTORS AND CANCER. THE EXAMPLE OF PAX GENES.

Pax genes encode for transcription factors important in cell differentiation and embryonic development. These genes are very much conserved in vertebrates and homologous genes are also present in lower eukaryotics. Pax genes are defined by the presence of the paired box, a sequence encoding for a protein domain able of sequence-specific DNA recognition. Full-length Pax protein control a large variety of developmental decisions. Mutations of Pax genes give rise to abnormal phenotypes both in human and mouse. Recently, various studies have revealed the role that Pax genes may have in human tumours. Both "in vitro" and "in vivo" assays demonstrate that these genes possess an oncogenic potential. Moreover, misexpression or structural alterations of these genes have been detected in several human tumours. Together with studies that have revealed the critical biochemical and biological properties of Pax proteins, in this review we focus on their relevance in human cancer and, in particular, on target genes that may mediate their biological effects. A systematic identification of genes which are targets of Pax proteins may have a great impact in understanding molecular basis of neoplastic disease.

Journal Article↗
PubMed1996

A molecular code dictates sequence-specific DNA recognition by homeodomains.

Most homeodomains bind to DNA sequences containing the motif 5'-TAAT-3'. The homeodomain of thyroid transcription factor 1 (TTF-1HD) binds to sequences containing a 5'-CAAG-3' core motif, delineating a new mechanism for differential DNA recognition by homeodomains. We investigated the molecular basis of the DNA binding specificity of TTF-1HD by both structural and functional approaches. As already suggested by the three-dimensional structure of TTF-1HD, the DNA binding specificities of the TTF-1, Antennapedia and Engrailed homeodomains, either wild-type or mutants, indicated that the amino acid residue in position 54 is involved in the recognition of the nucleotide at the 3' end of the core motif 5'-NAAN-3'. The nucleotide at the 5' position of this core sequence is recognized by the amino acids located in position 6, 7 and 8 of the TTF-1 and Antennapedia homeodomains. These data, together with previous suggestions on the role of amino acids in position 50, indicate that the DNA binding specificity of homeodomains can be determined by a combinatorial molecular code. We also show that some specific combinations of the key amino acid residues involved in DNA recognition do not follow a simple, additive rule.

Animals↗
PubMed1996

In the TTF-1 homeodomain the contribution of several amino acids to DNA recognition depends on the bound sequence.

The thyroid transcription factor-1 homeodomain (TTF-1HD) shows a peculiar DNA binding specificity, preferentially recognizing sequences containing the 5'-CAAG-3' core motif. Most other homeodomains instead recognize sites containing the 5'-TAAT-3' core motif. Here, we show that TTF-1HD efficiently recognizes another sequence, called D1, devoid of the 5'-CAAG-3' core motif. Different experimental approaches indicate that TTF-1HD contacts the D1 sequence in a manner which is different to that used to interact with sequences containing the 5'-CAAG-3' core motif. The binding activities that mutants of TTF-1HD display with the D1 sequence or with the sequence containing the 5'-CAAG-3' core motif indicate that the role of several DNA-contacting amino acids is different. In particular, during recognition of the D1 sequence, backbone-interacting amino acids not relevant in binding to sequences containing the 5'-CAAG-3' core motif play an important role. In the TTF-1HD, therefore, the contribution of several amino acids to DNA recognition depends on the bound sequence. These data indicate that although a common bonding network exists in all of the HD/DNA complexes, peculiarities important for DNA recognition may occur in single cases.

Amino Acids↗
PubMed1996

A network of specific minor-groove contacts is a common characteristic of paired-domain-DNA interactions.

Pax proteins are a family of transcription factors conserved during evolution and able to bind specific DNA sequences through a domain called a "paired domain'. The DNA-binding specificity of the Pax-8 paired domain was investigated. Site-selection experiments indicate that Pax-8 binds to a consensus sequence similar to those bound by Pax-2 and Pax-5. When consensus sequences of various paired domains are observed in light of recent structural studies describing paired-domain-DNA interaction [Xu, Rould, Jun, Desplan and Pabo (1995) Cell 80, 639-650], it appears that base-pairs contacted in the minor groove are conserved, while most of the base-pairs contacted in the major groove are not. Therefore a network of specific minor groove contacts is a common characteristic of paired-domain-DNA interactions. The functional importance of such a network was successfully tested by analysing the effect of consensus-based mutations on the Pax-8 binding site of the thyroglobulin promoter.

Animals↗
PubMed1995

Definition of the DNA-binding specificity of TTF-1 homeodomain by chromatographic selection of binding sequences.

The homeodomain of the thyroid transcription factor-1 (TTF-1HD) shows a peculiar DNA-binding specificity, preferentially recognizing sequences having the 5'-CAAG-3' core motif. In order to detail the DNA-binding specificity of this protein, a TTF-1HD-Sepharose column chromatography was used. A sequential selection and amplification of sequences was performed. TTF-1HD binding activity for selected and unselected sequences was measured. The presence of the 5'-CAAG-3' core motif was necessary, but not sufficient, to obtain the maximal binding activity for TTF-1HD. However, several of the selected sequences do not contain the 5'-CAAG-3' core motif and are bound by TTF-1HD only 2-fold less with respect to sequences bound with the highest affinity. Therefore, these data indicate that TTF-1HD specifically recognizes a spectrum of sequences wider than previously determined.

Base Sequence↗
PubMed1994

Sequence-specific DNA recognition by the thyroid transcription factor-1 homeodomain.

The molecular basis for the DNA binding specificity of the thyroid transcription factor 1 homeodomain (TTF-1HD) has been investigated. Methylation and ethylation interference experiments show that the TTF-1HD alone recapitulates the DNA binding properties of the entire protein. Studies carried out with mutant derivatives of TTF-1HD indicate a precise correspondence of some of its amino acid residues with specific bases in its binding site, allowing a crude orientation of the TTF-1HD within the protein-DNA complex. TTF-1HD shows an overall geometry of interaction with DNA similar to that previously observed for Antennapedia class HDs, even though the binding specificities of these two types of HDs are distinct. We demonstrate that the crucial difference between the binding sites of Antennapedia class and TTF-1 HDs is in the motifs 5'-TAAT-3', recognized by Antennapedia, and 5'-CAAG-3', preferentially bound by TTF-1. Furthermore, the binding of wild type and mutants TTF-1 HD to oligonucleotides containing either 5'-TAAT-3' or 5'-CAAG-3' indicate that only in the presence of the latter motif the Gln50 in TTF-1 HD is utilized for DNA recognition. Since the Gln at position 50 is an essential determinant for DNA binding specificity for several other HDs that bind to 5'-TAAT-3' containing sequences, we suggest that utilization by different HDs of key residues may depend on the sequence context and probably follows a precise hierarchy of contacts.

Antennapedia Homeodomain Protein↗
PubMed1993

Effect of salt concentration on TTF-1 HD binding to specific and non-specific DNA sequences.

The Thyroid Transcription factor 1 (TTF-1) recognizes specific DNA sequences by a Homeodomain (TTF-1 HD). The TTF-1 HD DNA-binding properties with both specific and non-specific DNA sequences were investigated. TTF-1 HD exists as a monomer in solution and as a monomer binds DNA. At 75 mM KCl, its relative binding affinity with a specific DNA sequence is about 50 fold higher than with a non-specific DNA sequence. Increase of KCl concentration reduces the apparent binding affinity both to specific and non-specific DNA sequences. However, non-specific binding is more sensitive than specific binding to the increase of salt concentration. When DNA-binding reactions are performed at temperature and salt concentration close to the intracellular environment, TTF-1 HD binds the specific sequence with an affinity at least 1000 fold higher respect to the non-specific sequence.

Animals↗
PubMedDate not supplied

Expression of Pax-8, p53 and bcl-2 in human benign and malignant thyroid diseases.

BACKGROUND: Immunohistochemical expression of the transcription factor Pax-8 in human thyroid diseases has never been investigated. The relationship between Pax-8, bcl-2 and p53 in thyroid neoplasms is also matter of interest. MATERIALS AND METHODS: Seventy-three thyroid tissue samples were evaluated for the expression of Pax-8, p53 and bcl-2 using the immunoperoxidase technique. The series included 11 follicular adenomas, 11 goitres, 23 papillary carcinomas, 16 follicular carcinomas, 6 undifferentiated carcinomas and 6 medullary carcinomas. RESULTS: The percentage of Pax-8 positive cells ranged from 14.9 to 27.1% and 10.1 to 39% in goitres and follicular adenomas, respectively. Among differentiated carcinomas, follicular histotype showed a Pax-8 immunoreactivity ranging from 0 to 26.5% of the neoplastic cells whereas in papillary carcinomas the percentage of positive cells ranged from 0 to 16.8%. None out of the six undifferentiated carcinomas showed Pax-8 immunoreactivity. The same negative pattern was noticed in medullary carcinomas. A statistically significant difference in Pax-8 expression was observed between non-malignant and malignant diseases (p < 0.0001). A different reactivity for Pax-8 was also noticed between differentiated carcinomas and undifferentiated carcinomas (p = 0.07). None of the benign tissues stained for p53 whereas among malignant specimens different percentages of p53 expression were observed with all undifferentiated carcinomas expressing the highest positivity (range 24.1-88.6%). Finally, when a combined analysis of bcl-2 and Pax-8 reactivity was carried out, some carcinomas proved to be Pax-8 negative and bcl-2 positive whereas others showed a similar immunoreactive pattern for both Pax-8 and bcl-2. CONCLUSIONS: Pax-8 is mainly expressed in benign rather than in malignant thyroid diseases and, among neoplasms, differentiated carcinomas express Pax-8 more frequently than undifferentiated carcinomas. An inverse pattern was observed for p53. Bcl-2 seems to be partially related to Pax-8 expression. However, a Pax-8 independent bcl-2 expression is also evident.

Adenocarcinoma, Follicular↗
PubMedDate not supplied

[The T index in the elderly with altered values of free thyroxine and/or thyrotropin. A new thyroid diagnostic-therapeutic index].

BACKGROUND: Routinary evaluation of FT4 and TSH, in elderly in-patients without thyroid disease shows frequent, isolated and, often unclear, changes from normal values of plasma TSH and FT4 concentrations. A new parameter called "T index" derived from the product of FT4 and TSH values has been used by the authors. In a previous work they studied "T index" variations in 1257 elderly subjects with normal FT4 and TSH levels. They have determined the "T index" theoretic model of distribution and identified a normality range (values from 5.78 to 50.76), a suspect range (values from 2.92 to 5.78 and from 50.76 to 68.6) and a pathologic range (values less than 2.92 and more than 68.6). Aim of this study was to investigate "T index" variations in a group of 357 elderly subjects with altered FT4 and/or TSH levels. METHODS: Patients were divided into eight groups according to different concentrations of FT4 and/or TSH levels. "T index" results were expressed as mean, standard deviation, maximum and minimum values. Patients were therefore divided into three groups (normality range, suspect range, pathologic range) according to "T index" distribution as previously described. RESULTS: In 20% of elderly people hospitalized, we found alterations of thyroid hormones levels represented mostly by: a) FT4 normal; TSH low. b) FT4 normal; TSH high, c) FT4 low; TSH normal. In case of hypothalamus-hypophysis hypothyroidism and in case of hyperthyroidism, "T index" score is, usually, less than 2.92, whereas in case of hypothalamus-hypophysis hypothyroidism and hypothyroidism "T index" score is, nearly always, more than 68.6. When TSH levels are into the range of normality "T index" score has always normality levels. The "T index" helps us to divide patients with subclinical hyperthyroidism into two groups: one with values from 5.78 to 2.92 (suspect range), and the other, with values less than 2.92 pathologic range). In patients with subclinical hypothyroidism, some patients have values from 50.76 to 68.6 (suspect range), other patients have values more than 68.6 (pathologic range). CONCLUSIONS: In case of subclinical hypothyroidism or subclinical hyperthyroidism the use of "T index" seems to be a good way to select the cases in which it is better to start pharmacological treatment (hormonal replacement or thyroid inhibition) from those which is better to follow-up.

Aged↗