Human Tat-specific factor 1 binds the HIV-1 genome and selectively transports HIV-1 RNAs.

Human immunodeficiency virus type 1 (HIV-1) propagation requires many human cofactors. Multiple groups have demonstrated that Tat-specific factor 1 (Tat-SF1) is an HIV-1 dependency factor. Depletion of this protein lowers HIV-1 infectivity, however, it does not affect the overall levels of viral RNA. Rather, Tat-SF1 regulates the relative levels of each RNA size class. This would be consistent with roles in splicing, transport, and/or stability of viral RNAs. We hypothesized that if Tat-SF1 plays any of these roles, then we should detect binding of the protein to the RNA genome. Furthermore, knocking down Tat-SF1 should result in altered RNA stability and/or localization in human cells. Fragments of the HIV-1 genome were used as RNA probes in electrophoretic mobility shift assays and fluorescence correlation spectroscopy experiments. Our results show that Tat-SF1 can form a complex with TAR RNA in vitro, independent of Tat. This factor interacts with at least one additional location in the 5' end of the HIV-1 genome. Tat seems to enhance the formation of this complex. To analyze HIV-1 RNA localization, HeLa cells with Tat-SF1 knocked down were also transfected with a proviral clone. RNA from nuclear and cytoplasmic fractions was purified, followed by RT-qPCR analysis. Tat-SF1 likely binds the HIV-1 RNA genome at TAR and potentially other locations and selectively transports HIV-1 RNAs, facilitating the unspliced RNA's nuclear export while retaining singly spliced RNAs in the nucleus. This is a novel role for this HIV-1 dependency factor.

Morphological Supports: Investigating Differences in How Morphological Knowledge Supports Reading Comprehension for Middle School Students With Limited Reading Vocabulary.

Purpose The current study takes a practical and theoretically grounded look at assessment of morphological knowledge and its potential to deepen understanding of how morphological knowledge supports reading comprehension for students with limited reading vocabulary. Specifically, we explore how different morphological skills support reading comprehension for students with typical reading vocabulary development compared to students with limited reading vocabulary. Method A sample of 1,140 fifth through eighth graders were assessed via a gamified, computer-adaptive measure of language that contained a morphological knowledge assessment. Links to standardized reading comprehension were explored with a focus on determining differences for the 184 students in the sample who showed limited reading vocabulary knowledge. Specifically, multiple regression analyses were used to test for the relation between morphology skills and standardized reading comprehension, as well as the moderator effect of reading vocabulary on the relation between morphological knowledge and standardized reading comprehension. Results Findings indicate that the four instructionally malleable morphological skills identified by the assessment differentially supported reading comprehension. These skills were (a) Morphological Awareness, (b) Syntactic Morphological Knowledge, (c) Semantic Morphological Knowledge, and (d) Phonological/Orthographic Morphological Knowledge. Significant interactions for students with limited reading vocabulary were shown in how the skills of Syntactic Morphological Knowledge, Semantic Morphological Knowledge, and Phonological/Orthographic Morphological Knowledge supported standardized Reading Comprehension. Conclusions Given the challenges students with limited reading vocabulary have with semantic information, Syntactic Morphological Knowledge and Phonological/Orthographic Morphological Knowledge were particularly supportive, suggesting the compensatory role of these morphological skills. In contrast, Semantic Morphological Knowledge had a negative relationship with Reading Comprehension for students with limited reading vocabulary. Implications for theory, research, and practice are discussed.

Exploring the Dimensionality of Morphological Knowledge for Adolescent Readers.

This study examined the dimensionality of morphological knowledge. The performance of 371 seventh- and eighth-graders on seven morphological knowledge tasks was investigated using confirmatory factor analysis. Results suggested that morphological knowledge was best fit by a bifactor model with a general factor of morphological knowledge and seven specific factors, representing tasks that tap different facets of morphological knowledge. Next, structural equation modelling was used to explore links to literacy outcomes. Results indicated the general factor and the specific factor of morphological meaning processing showed significant positive associations with reading comprehension and vocabulary. Also, the specific factor of generating morphologically related words showed significant positive associations with vocabulary, while specific factors of morphological word reading and spelling processing showed small negative relationships to reading comprehension and vocabulary. Findings highlight the complexity of morphological knowledge and suggest the importance of being cognizant of the nature of morphology when designing and interpreting studies.

Modeling Learning in Doubly Multilevel Binary Longitudinal Data Using Generalized Linear Mixed Models: An Application to Measuring and Explaining Word Learning.

When word learning is supported by instruction in experimental studies for adolescents, word knowledge outcomes tend to be collected from complex data structure, such as multiple aspects of word knowledge, multilevel reader data, multilevel item data, longitudinal design, and multiple groups. This study illustrates how generalized linear mixed models can be used to measure and explain word learning for data having such complexity. Results from this application provide deeper understanding of word knowledge than could be attained from simpler models and show that word knowledge is multidimensional and depends on word characteristics and instructional contexts.

Modeling Polymorphemic Word Recognition: Exploring Differences Among Children With Early-Emerging and Late-Emerging Word Reading Difficulty.

Comprehensive models of derived polymorphemic word recognition skill in developing readers, with an emphasis on children with reading difficulty (RD), have not been developed. The purpose of the present study was to model individual differences in polymorphemic word recognition ability at the item level among 5th-grade children (N = 173) oversampled for children with RD using item-response crossed random-effects models. We distinguish between two subtypes of RD children with word recognition problems, those with early-emerging RD and late-emerging RD. An extensive set of predictors representing item-specific knowledge, child-level characteristics, and word-level characteristics were used to predict item-level variance in polymorphemic word recognition. Results indicate that item-specific root word recognition and word familiarity; child-level RD status, morphological awareness, and orthographic choice; word-level frequency and root word family size; and the interactions between morphological awareness and RD status and root word recognition and root transparency predicted individual differences in polymorphemic word recognition item performance. Results are interpreted within a multisource individual difference model of polymorphemic word recognition skill spanning item-specific, child-level, and word-level knowledge.

Morphological knowledge and literacy acquisition.

The purpose of this special issue of the Journal of Learning Disabilities is to bring to the attention of researchers and educators studies on morphology and literacy that either involve students with learning difficulties or have educational implications for teaching such students. In our introduction, we first provide background information about morphological knowledge and consider the role of morphology in literacy, focusing on findings that are relevant for instruction of students who struggle with reading and writing. Next we present an overview of the studies included in this issue, organized by current issues concerning the role of morphological knowledge in literacy. Collectively, the articles in this issue suggest that students with weaker literacy skills tend to lag behind their peers in morphological knowledge but that all students are likely to benefit from morphological instruction. Morphological interventions hold promise, especially for students who face challenges in language learning and literacy, but additional research is needed to provide a basis for informed decisions about the design of effective morphological interventions.

Multisyllabic word reading as a moderator of morphological awareness and reading comprehension.

The purpose of this study was to investigate whether the relation between morphological awareness on reading comprehension is moderated by multisyllabic word reading ability in fifth-grade students (N = 169, 53.7% female, 65.2% minority status, 69.2% free/reduced lunch status), oversampled for poor reading skill, when controlling for general knowledge and vocabulary. Based on the lexical quality hypothesis, it was expected that morphological awareness would have a stronger effect on comprehension for children with poor word reading skills, suggesting possible use of morphological awareness for word identification support. Results indicated that neither morphological awareness nor word reading was uniquely associated with reading comprehension when both were included in the model along with vocabulary and general knowledge. Instead, the interaction between word reading and morphological awareness explained significant additional variance in reading comprehension. By probing this interaction, it was determined that the effect of morphological awareness on reading comprehension was significant for the 39% of the sample that had more difficulty reading multisyllabic words but not for students at the higher end of the multisyllabic word reading continuum. We conclude from these results that the relation between morphological awareness and reading comprehension is moderated by multisyllabic word reading ability, providing support for the lexical quality hypothesis. Although we have only correlational data, we suggest tentative instructional practices for improving the reading skill of upper elementary struggling readers.

Explanatory multidimensional multilevel random item response model: an application to simultaneous investigation of word and person contributions to multidimensional lexical representations.

This paper presents an explanatory multidimensional multilevel random item response model and its application to reading data with multilevel item structure. The model includes multilevel random item parameters that allow consideration of variability in item parameters at both item and item group levels. Item-level random item parameters were included to model unexplained variance remaining when item related covariates were used to explain variation in item difficulties. Item group-level random item parameters were included to model dependency in item responses among items having the same item stem. Using the model, this study examined the dimensionality of a person's word knowledge, termed lexical representation, and how aspects of morphological knowledge contributed to lexical representations for different persons, items, and item groups.

A meta-analysis of morphological interventions: effects on literacy achievement of children with literacy difficulties.

This study synthesizes 79 standardized mean-change differences between control and treatment groups from 17 independent studies, investigating the effect of morphological interventions on literacy outcomes for students with literacy difficulties. Average total sample size ranged from 15 to 261 from a wide range of grade levels. Overall, morphological instruction showed a significant improvement on literacy achievement (d = 0.33). Specifically, its effect was significant on several literacy outcomes such as phonological awareness (d = 0.49), morphological awareness (d = 0.40), vocabulary (d = 0.40), reading comprehension (d = 0.24), and spelling (d = 0.20). Morphological instruction was particularly effective for children with reading, learning, or speech and language disabilities, English language learners, and struggling readers, suggesting the possibility that morphological instruction can remediate phonological processing challenges. Other moderators were also explored to explain differences in morphological intervention effects. These findings suggest students with literacy difficulties would benefit from morphological instruction.